Risoluzione dei problemi di DHCP esterno su VPN VxLAN Cat9000
Sommario
Introduzione
Questo documento descrive come risolvere i problemi DHCP in ambienti VxLAN VPN esterni sulle piattaforme Cat9000.
Prerequisiti
Requisiti
Cisco raccomanda la conoscenza dei seguenti argomenti:
- LAN virtuale estendibile su piattaforme Cat9000
- Individuazione dei protocolli di configurazione host in ambienti VxLAN
- Border Gateway Protocol (BGP)
Per ulteriori informazioni su questi argomenti, consultare:
- Capitolo: Configurazione dell'inoltro DHCP in un VXLAN BGP Cat9300
- Capitolo: Configurazione dell'inoltro DHCP in un VPN BGP VXLAN Fabric Cat9400
- Capitolo: Configurazione dell'inoltro DHCP in un VXLAN BGP Cat9500
- Capitolo: Configurazione dell'inoltro DHCP in un VXLAN BGP Cat9600
Componenti usati
Il riferimento delle informazioni contenute in questo documento è il software Cisco IOS XE.
Le informazioni discusse in questo documento fanno riferimento a dispositivi usati in uno specifico ambiente di emulazione. Su tutti i dispositivi menzionati nel documento la configurazione è stata ripristinata ai valori predefiniti. Se la rete è operativa, valutare attentamente eventuali conseguenze derivanti dall'uso dei comandi.
Esempio di rete
Topologia VxLAN DHCP
Studio del caso 1: Impossibile ottenere un indirizzo IP dal server esterno (gateway centralizzato all'interno dell'infrastruttura)
Questa topologia utilizza il VxLAN Layer 2 per la VLAN 250. L'host richiede gli indirizzi IP del server DHCP esterno.
Verifica Leaf-01
Passaggio 1. In Foglia-1, verificare l'apprendimento dell'indirizzo MAC per gli host locali.
Passaggio 2. Confermare inoltre che l'indirizzo MAC del gateway predefinito sia stato appreso. Verificare che gli indirizzi MAC appresi e l'indirizzo IP del gateway predefinito siano installati correttamente come voci nella tabella BGP.
Leaf-1#show mac address-table address 10b3.d68b.3be3 (host mac address)
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
250 10b3.d68b.3be3 DYNAMIC Twe1/0/1
Centralized-Gateway#show interface vlan 250 | include bia (remote mac address)
Hardware is Ethernet SVI, address is 3473.2db8.bee3 (bia 3473.2db8.bee3)
Leaf-1#show bgp l2vpn evpn 10b3.d68b.3be3 (local mac address)
BGP routing table entry for [2][203.0.113.1:250][0][48][10B3D68B3BE3][0][*]/20, version 3
Paths: (1 available, best #1, table evi_250)
Advertised to update-groups:
2
Refresh Epoch 1
Local
0.0.0.0 (via default) from 0.0.0.0 (203.0.113.1)
Origin incomplete, localpref 100, weight 32768, valid, sourced, local, best
EVPN ESI: 00000000000000000000, Label1 10250
Extended Community: RT:10:250 ENCAP:8
Local irb vxlan vtep:
vrf:not found, l3-vni:0
local router mac:0000.0000.0000
core-irb interface:(not found)
vtep-ip:203.0.113.1
rx pathid: 0, tx pathid: 0x0
Updated on Oct 14 2025 22:27:32 UTC
Leaf-1#show bgp l2vpn evpn 3473.2db8.bee3 (remote mac address)
BGP routing table entry for [2][203.0.113.1:250][0][48][34732DB8BEE3][32][192.0.2.254]/24, version 9
Paths: (1 available, best #1, table evi_250)
Flag: 0x100
Not advertised to any peer
Refresh Epoch 4
Local, imported path from [2][203.0.113.4:250][0][48][34732DB8BEE3][32][192.0.2.254]/24 (global)
203.0.113.4 (metric 3) (via default) from 203.0.113.3 (203.0.113.3)
Origin incomplete, metric 0, localpref 100, valid, internal, best
EVPN ESI: 00000000000000000000, Label1 10250
Extended Community: RT:10:250 ENCAP:8 EVPN DEF GW:0:0
Originator: 203.0.113.4, Cluster list: 203.0.113.3
rx pathid: 0, tx pathid: 0x0
Updated on Oct 14 2025 14:48:35 UTC
BGP routing table entry for [2][203.0.113.4:250][0][48][34732DB8BEE3][32][192.0.2.254]/24, version 8
Paths: (1 available, best #1, table EVPN-BGP-Table)
Flag: 0x100
Not advertised to any peer
Refresh Epoch 4
Local
203.0.113.4 (metric 3) (via default) from 203.0.113.3 (203.0.113.3)
Origin incomplete, metric 0, localpref 100, valid, internal, best
EVPN ESI: 00000000000000000000, Label1 10250
Extended Community: RT:10:250 ENCAP:8 EVPN DEF GW:0:0
Originator: 203.0.113.4, Cluster list: 203.0.113.3
rx pathid: 0, tx pathid: 0x0
Updated on Oct 14 2025 14:48:35 UTC
Passaggio 3. Convalidare l'apprendimento dell'indirizzo MAC tra Foglia-1 e Gateway predefinito. Leaf-1 apprende gli indirizzi MAC locali tramite la porta trunk e gli indirizzi MAC remoti tramite BGP.
Leaf-1#show l2route evpn mac
EVI ETag Prod Mac Address Next Hop(s) Seq Number
----- ---------- ----- -------------- ---------------------------------------------------- ----------
250 0 L2VPN 10b3.d68b.3b81 Twe1/0/1:250 0
250 0 L2VPN 10b3.d68b.3be3 Twe1/0/1:250 0 (Host local mac address)
250 0 BGP 3473.2db8.bee3 V:10250 203.0.113.4 0 (CGW SVI mac address)
Passaggio 4. Verificare l'apprendimento del gateway predefinito sullo switch Leaf-1 all'interno dell'istanza EVPN L2VPN.
Leaf-1#show l2vpn evpn default-gateway
Valid Default Gateway Address EVI VLAN MAC Address Source
----- --------------------------------------- ----- ----- -------------- -----------
Y 192.0.2.254 250 250 3473.2db8.bee3 203.0.113.4
Passaggio 5. Se la prospettiva VxLAN è corretta, procedere con DHCP per risolvere il problema.
Passaggio 6. Confermare il processo DORA da Leaf-1 al gateway DHCP. In Leaf-01, abilitare il debug del pacchetto di snooping ip dhcp e verificare se il rilevamento genera voci nel log. Se non si verifica la generazione del registro, abilitare le acquisizioni dei pacchetti sull'interfaccia che si connette al PC.
Leaf-1#debug ip dhcp snooping packet
DHCP Snooping Packet debugging is on
Leaf-1#
*Oct 21 19:33:16.358: DHCP_SNOOPING: received new DHCP packet from input interface (TwentyFiveGigE1/0/1)
*Oct 21 19:33:16.358: DHCP Memory dump is printed for process packet
<snip>
*Oct 21 19:33:16.367: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Twe1/0/1, MAC da: ffff.ffff.ffff, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: -1865499306, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Oct 21 19:33:16.367: DHCP_SNOOPING: add relay information option.
*Oct 21 19:33:16.367: DHCP_SNOOPING: Encoding opt82 CID in vlan-mod-port format
*Oct 21 19:33:16.367: DHCP_SNOOPING:VxLAN : vlan_id 250 VNI 10250 mod 1 port 1
*Oct 21 19:33:16.367: DHCP_SNOOPING: Encoding opt82 RID in MAC address format
*Oct 21 19:33:16.367: DHCP_SNOOPING: binary dump of relay info option, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x1 0x1 0x0 0x0 0x2 0x8 0x0 0x6 0x4C 0x5D 0x3C 0xEB 0x43 0x40
*Oct 21 19:33:16.367: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Oct 21 19:33:16.367: DHCP_SNOOPING: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (250)
*Oct 21 19:33:16.367: DHCP_SNOOPING: L2RELAY: sent unicast packet to default gw: 3473.2db8.bee3 vlan 0 src intf TwentyFiveGigE1/0/1
*Oct 21 19:33:20.058: DHCP_SNOOPING: received new DHCP packet from input interface (TwentyFiveGigE1/0/1)
*Oct 21 19:33:20.058: DHCP Memory dump is printed for process packet
Passaggio 7. Se il debug non viene attivato, acquisire il pacchetto per la convalida. Utilizzare la sintassi specificata per acquisire i pacchetti di individuazione in entrata:
monitor capture <name> interface <int> in match ipv4 protocol udp any range 67 68 any range 67 68 start
monitor capture <name> stop
monitor capture export file flash:<name>.pcap
show monitor capture <name> buffer display-filter "eth.addr==[mac address]" detailed
Nota: Acquisire le stringhe del filtro di visualizzazione conformi alla sintassi del filtro Wireshark.
Leaf-1#monitor capture cap interface twe1/0/1 in match ipv4 protocol udp any range 67 68 any range 67 68 start
Started capture point : cap
Leaf-1#
*Oct 21 22:57:04.719: %BUFCAP-6-ENABLE: Capture Point cap enabled.
Leaf-1#
Leaf-1#monitor capture cap stop
Capture statistics collected at software:
Capture duration - 96 seconds
Packets received - 10
Packets dropped - 0
Packets oversized - 0
Bytes dropped in asic - 0
Capture buffer will exists till exported or cleared
Stopped capture point : cap
*Oct 21 22:58:40.810: %BUFCAP-6-DISABLE: Capture Point cap disabled.
Leaf-1#show monitor capture cap buffer display-filter "eth,addr==10:b3:d6:8b:3b:e3" detailed
Starting the packet display ........ Press Ctrl + Shift + 6 to exit
Frame 1: 371 bytes on wire (2968 bits), 371 bytes captured (2968 bits) on interface /tmp/epc_ws/wif_to_ts_pipe, id 0
Interface id: 0 (/tmp/epc_ws/wif_to_ts_pipe)
Interface name: /tmp/epc_ws/wif_to_ts_pipe
Encapsulation type: Ethernet (1)
Arrival Time: Oct 21, 2025 22:57:07.843851000 UTC
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1761087427.843851000 seconds
<snip>
[Protocols in frame: eth:ethertype:vlan:ethertype:ip:udp:dhcp]
Ethernet II, Src: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3), Dst: ff:ff:ff:ff:ff:ff (ff:ff:ff:ff:ff:ff)
Destination: ff:ff:ff:ff:ff:ff (ff:ff:ff:ff:ff:ff)
Address: ff:ff:ff:ff:ff:ff (ff:ff:ff:ff:ff:ff)
.... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
.... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
Source: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 250
000. .... .... .... = Priority: Best Effort (default) (0)
...0 .... .... .... = DEI: Ineligible
.... 0000 1111 1010 = ID: 250
Type: IPv4 (0x0800)
<snip>
User Datagram Protocol, Src Port: 68, Dst Port: 67
Source Port: 68
Destination Port: 67
Length: 333
Checksum: 0xdf55 [unverified]
[Checksum Status: Unverified]
[Stream index: 0]
[Timestamps]
[Time since first frame: 0.000000000 seconds]
[Time since previous frame: 0.000000000 seconds]
Dynamic Host Configuration Protocol (Discover)
Message type: Boot Request (1)
Hardware type: Ethernet (0x01)
Hardware address length: 6
Hops: 0
Transaction ID: 0x3bd7aadb
Seconds elapsed: 7
Bootp flags: 0x8000, Broadcast flag (Broadcast)
1... .... .... .... = Broadcast flag: Broadcast
.000 0000 0000 0000 = Reserved flags: 0x0000
Client IP address: 0.0.0.0
Your (client) IP address: 0.0.0.0
Next server IP address: 0.0.0.0
Relay agent IP address: 0.0.0.0
Client MAC address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Option: (53) DHCP Message Type (Discover)
<snip>
Passaggio 8. Convalidare l'incapsulamento dei pacchetti VxLAN tramite l'acquisizione dei pacchetti. Applicare diversi filtri per questa convalida. VxLAN utilizza la porta UDP 4789.
monitor capture cap interface <outgoing interface > out match ipv4 protocol udp any any eq 4789 (Interface that is pointing to the RR or VTEP via BGP)
Leaf-1#show ip bgp all summary
For address family: L2VPN E-VPN
<snip>
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
203.0.113.3 4 10 4204 4122 365 0 0 2d13h 2
Leaf-1#show ip route 203.0.113.3
Routing entry for 203.0.113.3/32
Known via "ospf 1", distance 110, metric 2, type intra area
Last update from 172.x.x.2 on TwentyFiveGigE1/0/2, 2d13h ago
Routing Descriptor Blocks:
* 172.x.x.2, from 203.0.113.3, 2d13h ago, via TwentyFiveGigE1/0/2
Leaf-1#monitor capture cap interface twe1/0/2 out match ipv4 protocol udp any any eq 4789 start
*Oct 21 23:51:07.689: %BUFCAP-6-ENABLE: Capture Point cap enabled.
Leaf-1#show monitor capture cap buffer display-filter "eth.addr==10:b3:d6:8b:3b:e3" detailed
Starting the packet display ........ Press Ctrl + Shift + 6 to exit
Frame 1: 443 bytes on wire (3544 bits), 443 bytes captured (3544 bits) on interface /tmp/epc_ws/wif_to_ts_pipe, id 0
Interface id: 0 (/tmp/epc_ws/wif_to_ts_pipe)
Interface name: /tmp/epc_ws/wif_to_ts_pipe
Encapsulation type: Ethernet (1)
Arrival Time: Oct 21, 2025 23:51:34.848693000 UTC
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1761090694.848693000 seconds
<snip>
[Protocols in frame: eth:ethertype:ip:udp:vxlan:eth:ethertype:ip:udp:dhcp]
Ethernet II, Src: 00:00:00:00:00:00 (00:00:00:00:00:00), Dst: 00:00:00:00:00:00 (00:00:00:00:00:00)
Destination: 00:00:00:00:00:00 (00:00:00:00:00:00)
Address: 00:00:00:00:00:00 (00:00:00:00:00:00)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: 00:00:00:00:00:00 (00:00:00:00:00:00)
Address: 00:00:00:00:00:00 (00:00:00:00:00:00)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 203.0.113.1, Dst: 203.0.113.4
0100 .... = Version: 4
.... 0101 = Header Length: 20 bytes (5)
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
0000 00.. = Differentiated Services Codepoint: Default (0)
.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
<snip>
User Datagram Protocol, Src Port: 65479, Dst Port: 4789
Source Port: 65479
Destination Port: 4789
Length: 409
[Checksum: [missing]]
[Checksum Status: Not present]
[Stream index: 0]
[Timestamps]
[Time since first frame: 0.000000000 seconds]
[Time since previous frame: 0.000000000 seconds]
Virtual eXtensible Local Area Network
Flags: 0x0800, VXLAN Network ID (VNI)
0... .... .... .... = GBP Extension: Not defined
.... .... .0.. .... = Don't Learn: False
.... 1... .... .... = VXLAN Network ID (VNI): True
.... .... .... 0... = Policy Applied: False
.000 .000 0.00 .000 = Reserved(R): 0x0000
Group Policy ID: 0
VXLAN Network Identifier (VNI): 10250
Reserved: 0
<snip>
User Datagram Protocol, Src Port: 68, Dst Port: 67
Source Port: 68
Destination Port: 67
Length: 359
Checksum: 0x767d [unverified]
[Checksum Status: Unverified]
[Stream index: 1]
[Timestamps]
[Time since first frame: 0.000000000 seconds]
[Time since previous frame: 0.000000000 seconds]
Dynamic Host Configuration Protocol (Discover)
Message type: Boot Request (1)
Hardware type: Ethernet (0x01)
Hardware address length: 6
Hops: 0
Transaction ID: 0xd4c42ec1
Seconds elapsed: 0
Bootp flags: 0x8000, Broadcast flag (Broadcast)
1... .... .... .... = Broadcast flag: Broadcast
.000 0000 0000 0000 = Reserved flags: 0x0000
Client IP address: 0.0.0.0
Your (client) IP address: 0.0.0.0
Next server IP address: 0.0.0.0
Relay agent IP address: 0.0.0.0
Client MAC address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Verifica gateway centralizzata
Passaggio 1. Convalidare l'indirizzo MAC dell'host appreso sulle route BGP e EVPN L2 (questo passaggio rispecchia la procedura di verifica Leaf iniziale).
Centralized-Gateway#show bgp l2vpn evpn 10b3.d68b.3be3 (remote host mac address)
BGP routing table entry for [2][203.0.113.1:250][0][48][10B3D68B3BE3][0][*]/20, version 12
Paths: (1 available, best #1, table EVPN-BGP-Table)
Not advertised to any peer
Refresh Epoch 1
Local
203.0.113.1 (metric 3) (via default) from 203.0.113.3 (203.0.113.3) (learned via RR)
Origin incomplete, metric 0, localpref 100, valid, internal, best
EVPN ESI: 00000000000000000000, Label1 10250
Extended Community: RT:10:250 ENCAP:8
Originator: 203.0.113.1, Cluster list: 203.0.113.3
rx pathid: 0, tx pathid: 0x0
Updated on Oct 27 2025 17:53:37 UTC
BGP routing table entry for [2][203.0.113.4:250][0][48][10B3D68B3BE3][0][*]/20, version 14
Paths: (1 available, best #1, table evi_250)
Not advertised to any peer
Refresh Epoch 1
Local, imported path from [2][203.0.113.1:250][0][48][10B3D68B3BE3][0][*]/20 (global)
203.0.113.1 (metric 3) (via default) from 203.0.113.3 (203.0.113.3)
Origin incomplete, metric 0, localpref 100, valid, internal, best
EVPN ESI: 00000000000000000000, Label1 10250
Extended Community: RT:10:250 ENCAP:8
Originator: 203.0.113.1, Cluster list: 203.0.113.3
rx pathid: 0, tx pathid: 0x0
Updated on Oct 27 2025 17:53:37 UTC
Centralized-Gateway#show l2route evpn mac mac-address 10b3.d68b.3be3
EVI ETag Prod Mac Address Next Hop(s) Seq Number
----- ---------- ----- -------------- ---------------------------------------------------- ----------
250 0 BGP 10b3.d68b.3be3 V:10250 203.0.113.1 0
Passaggio 2. Verificare le informazioni sull'inoltro DHCP e la configurazione dello snooping DHCP sul gateway centralizzato.
Centralized-Gateway#show running-config | section dhcp
ip dhcp-relay source-interface Loopback0
ip dhcp relay information option vpn
ip dhcp relay information option
ip dhcp compatibility suboption link-selection standard
ip dhcp compatibility suboption server-override standard
ip dhcp snooping vlan 250
ip dhcp snooping
Passaggio 3. Verificare la connettività al server DHCP e avviare il ping dall'interfaccia VLAN 250.
Centralized-Gateway#ping 198.51.100.10 source vlan 250
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 198.51.100.10, timeout is 2 seconds:
Packet sent with a source address of 192.0.2.254
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
Passaggio 4. Eseguire l'acquisizione di un pacchetto per verificare se i messaggi Discovery provenienti dagli host remoti raggiungono il gateway centralizzato.
Centralized-Gateway#monitor capture cap interface vlan250 in match ipv4 protocol udp any range 67 68 any range 67 68
Centralized-Gateway#monitor capture cap start
Started capture point : cap
Centralized-Gateway#show monitor capture cap buffer display-filter "eth.addr==10:b3:d6:8b:3b:e3" detailed
Starting the packet display ........ Press Ctrl + Shift + 6 to exit
Frame 1: 401 bytes on wire (3208 bits), 401 bytes captured (3208 bits) on interface /tmp/epc_ws/wif_to_ts_pipe, id 0
Interface id: 0 (/tmp/epc_ws/wif_to_ts_pipe)
Interface name: /tmp/epc_ws/wif_to_ts_pipe
Encapsulation type: Ethernet (1)
Arrival Time: Oct 27, 2025 20:43:30.774923000 UTC
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1761597810.774923000 seconds
<snip>
[Protocols in frame: eth:ethertype:cmd:ethertype:ip:udp:dhcp]
Ethernet II, Src: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3), Dst: 34:73:2d:b8:be:e3 (34:73:2d:b8:be:e3)
Destination: 34:73:2d:b8:be:e3 (34:73:2d:b8:be:e3)
Address: 34:73:2d:b8:be:e3 (34:73:2d:b8:be:e3)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: CiscoMetaData (0x8909)
<snip>
Internet Protocol Version 4, Src: 0.0.0.0, Dst: 255.255.255.255
0100 .... = Version: 4
.... 0101 = Header Length: 20 bytes (5)
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
0000 00.. = Differentiated Services Codepoint: Default (0)
.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
Total Length: 379
Identification: 0x0230 (560)
Flags: 0x00
0... .... = Reserved bit: Not set
.0.. .... = Don't fragment: Not set
..0. .... = More fragments: Not set
Fragment Offset: 0
Time to Live: 255
Protocol: UDP (17)
Header Checksum: 0xb842 [validation disabled]
[Header checksum status: Unverified]
Source Address: 0.0.0.0
Destination Address: 255.255.255.255
User Datagram Protocol, Src Port: 68, Dst Port: 67
Source Port: 68
Destination Port: 67
Length: 359
Checksum: 0x8f64 [unverified]
[Checksum Status: Unverified]
[Stream index: 0]
[Timestamps]
[Time since first frame: 0.000000000 seconds]
[Time since previous frame: 0.000000000 seconds]
UDP payload (351 bytes)
Dynamic Host Configuration Protocol (Discover)
Message type: Boot Request (1)
Hardware type: Ethernet (0x01)
Hardware address length: 6
Hops: 0
Transaction ID: 0xf23af863
Seconds elapsed: 0
Bootp flags: 0x8000, Broadcast flag (Broadcast)
1... .... .... .... = Broadcast flag: Broadcast
.000 0000 0000 0000 = Reserved flags: 0x0000
Client IP address: 0.0.0.0
Your (client) IP address: 0.0.0.0
Next server IP address: 0.0.0.0
Relay agent IP address: 0.0.0.0
Client MAC address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Option: (53) DHCP Message Type (Discover)
Length: 1
DHCP: Discover (1)
Option: (57) Maximum DHCP Message Size
Length: 2
Maximum DHCP Message Size: 1200
Option: (61) Client identifier
Length: 27
Type: 0
Client Identifier: cisco-10b3.d68b.3be3-Vl250
<snip>
Passaggio 5. Eseguire un'acquisizione successiva del pacchetto sullo switch. Verificare l'uscita di Discovery e l'entrata dell'offerta.
Centralized-Gateway#no monitor capture cap
Centralized-Gateway#monitor capture cap interface vlan 75 both match ipv4 protocol udp any range 67 68 any range 67 68
Centralized-Gateway#monitor capture cap start
Started capture point : cap
Centralized-Gateway#monitor capture cap stop
Capture statistics collected at software:
Capture duration - 78 seconds
Packets received - 0
Packets dropped - 0
Packets oversized - 0
Bytes dropped in asic - 0
Passaggio 6. Se l'acquisizione del pacchetto non mostra pacchetti, procedere con il debug DHCP e convalidare lo stato del pacchetto sulla piattaforma.
Centralized-Gateway#debug ip dhcp snooping packet
<snip>
*Oct 27 22:20:24.444: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Tu0, MAC da: 3473.2db8.bee3, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: -1137609462, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Oct 27 22:20:24.445: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Oct 27 22:20:24.445: DHCP_SNOOPING: Packet destined to SVI Mac:3473.2db8.bee3
*Oct 27 22:20:24.445: DHCP_SNOOPING: bridge packet send packet to cpu port: Vlan250.
*Oct 27 22:20:24.445: DHCP_SNOOPING: bridge packet send packet to port: GigabitEthernet1/0/2, pak_vlan 250.
*Oct 27 22:20:27.952: DHCP_SNOOPING: received new DHCP packet from input interface (Tunnel0)
*Oct 27 22:20:27.952: DHCP Memory dump is printed for process packet.
Centralized-Gateway#debug ip dhcp server packet detail
*Oct 27 22:27:58.009: DHCPD: BOOTREQUEST from 0063.6973.636f.2d31.3062.332e.6436.3862.2e33.6265.332d.566c.3235.30 forwarded to 198.51.100.10.
*Oct 27 22:28:02.008: DHCPD: tableid for 192.0.2.254 on Vlan250 is 0
*Oct 27 22:28:02.008: DHCPD: client's VPN is .
*Oct 27 22:28:02.008: DHCPD: No option 125
*Oct 27 22:28:02.008: DHCPD: Option 124: Vendor Class Information
*Oct 27 22:28:02.008: DHCPD: Enterprise ID: 9
*Oct 27 22:28:02.008: DHCPD: Vendor-class-data-len: 13
*Oct 27 22:28:02.008: DHCPD: Data: 43393330304C2D3234502D3447
*Oct 27 22:28:02.008: DHCPD: Option 125 not present in the msg.
*Oct 27 22:28:02.008: DHCPD: Option 125 not present in the msg.
*Oct 27 22:28:02.008: DHCPD: Looking up binding using address 192.0.2.254
*Oct 27 22:28:02.008: DHCPD: setting giaddr to 192.0.2.254.
*Oct 27 22:28:02.008: DHCPD: relay information option before replacing suboptions
*Oct 27 22:28:02.008: DHCPD: 5218010c010a00080000280a01010000020800064c5d3ceb4340
*Oct 27 22:28:02.008: DHCPD: replacing suboptions in relay information option.
*Oct 27 22:28:02.008: DHCPD: relay information option content (add/replace):
*Oct 27 22:28:02.008: DHCPD: 52060504c00002fe
*Oct 27 22:28:02.008: DHCPD: giaddr changed to 203.0.113.4
Passaggio 7. Verificare che le interfacce che si connettono al server DHCP includano il comando specificato (in modo da evitare il rilascio del pacchetto DHCP).
Centralized-Gateway#sh running-config interface gi1/0/2
Building configuration...
Current configuration : 149 bytes
!
interface GigabitEthernet1/0/2
description to L2_switch
switchport trunk allowed vlan 75,250
switchport mode trunk
ip dhcp snooping trust
end
Nota: il comando ip dhcp snooping trust si applica solo alle interfacce trunk di layer 2.
Soluzione del problema
La configurazione della VxLAN funziona come previsto. Il server DHCP inoltra tuttavia le risposte DHCP all'indirizzo IP 203.0.113.4. Il server DHCP non è raggiungibile con questo indirizzo IP. La mancanza di connettività ha causato la perdita di pacchetti unicast nel gateway centralizzato.
Per risolvere il problema, è stata configurata una nuova interfaccia di loopback 1 ed è stata stabilita una route per l'indirizzo IP per fornire connettività con questo indirizzo di relay di loopback.
Log DHCP:
DHCP-Server#debug ip dhcp server packet detail
DHCP server packet detail debugging is on.
*Oct 28 00:23:43.464: DHCPD: DHCPDISCOVER received from client 0063.6973.636f.2d31.3062.332e.6436.3862.2e33.6265.332d.566c.3235.30 through relay 203.0.113.4.DHCPD: Setting only requested parameters
*Oct 28 00:23:43.464: DHCPD: Option 125 not present in the msg.
*Oct 28 00:23:43.465: DHCPD: egress Interfce GigabitEthernet0/0/4.75
*Oct 28 00:23:43.465: DHCPD: unicasting BOOTREPLY for client 10b3.d68b.3be3 to relay 203.0.113.4.
DHCP-Server#ping 203.0.113.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 203.0.113.4, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
DHCP-Server#
Gateway centralizzato: Configurare la connettività alla nuova interfaccia di loopback per la funzione di inoltro.
Centralized-Gateway#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Centralized-Gateway(config)#interface loopback 1
Centralized-Gateway(config-if)#ip address 198.51.100.25 255.255.255.255
Centralized-Gateway(config-if)#router eigrp 1
Centralized-Gateway(config-router)#network 198.51.100.25 0.0.0.0
Centralized-Gateway(config-router)#exit
Centralized-Gateway(config)#no ip dhcp-relay source-interface Loopback0
Centralized-Gateway(config)#ip dhcp-relay source-interface Loopback1
DHCP-Server#ping 198.51.100.25
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 198.51.100.25, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/9 ms
DHCP-Server#
Studio del caso 2: Impossibile ottenere un indirizzo IP dal server esterno (gateway centralizzato esterno all'infrastruttura)
Questa topologia utilizza il layer 2 VXLAN per la VLAN 250. L'host ottiene il proprio indirizzo IP da un server DHCP esterno all'infrastruttura.
Topologia VxLAN DHCP esterna
Verifica Leaf-01
Passaggio 1. In Foglia-1, verificare l'annuncio corretto sul gateway predefinito. Poiché il server DHCP si trova all'esterno del fabric VxLAN, è un requisito chiave per la corretta funzionalità dell'assegnazione dell'indirizzo IP.
Leaf-1#show l2vpn evpn default-gateway
Valid Default Gateway Address EVI VLAN MAC Address Source
----- --------------------------------------- ----- ----- -------------- -----------
Passaggio 2. Se l'output precedente è vuoto, procedere con la risoluzione dei problemi DHCP. Verificare che le configurazioni dello snooping DHCP appropriate siano presenti nei dispositivi foglia.
Leaf-1#show running-config | section dhcp
ip dhcp relay information option vpn
ip dhcp relay information option
ip dhcp compatibility suboption link-selection standard
ip dhcp compatibility suboption server-override standard
ip dhcp snooping vlan 250
ip dhcp snooping
Leaf-2#show running-config | section dhcp
ip dhcp relay information option vpn
ip dhcp relay information option
ip dhcp compatibility suboption link-selection standard
ip dhcp compatibility suboption server-override standard
ip dhcp snooping vlan 250
ip dhcp snooping
Passaggio 3. Se un dispositivo richiede attivamente un indirizzo IP tramite DHCP, abilitare il comando di debug appropriato per convalidare lo stato del pacchetto sulla piattaforma.
*Dec 6 22:42:19.568: DHCP_SNOOPING: received new DHCP packet from input interface (TwentyFiveGigE1/0/1)
*Dec 6 22:42:19.568: DHCP Memory dump is printed for process packet
<snip>
*Dec 6 22:42:19.578: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Twe1/0/1, MAC da: ffff.ffff.ffff, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: 1984524378, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 6 22:42:19.578: DHCP_SNOOPING: add relay information option.
*Dec 6 22:42:19.578: DHCP_SNOOPING: Encoding opt82 CID in vlan-mod-port format
*Dec 6 22:42:19.578: DHCP_SNOOPING:VxLAN : vlan_id 250 VNI 10250 mod 1 port 1
*Dec 6 22:42:19.578: DHCP_SNOOPING: Encoding opt82 RID in MAC address format
*Dec 6 22:42:19.578: DHCP_SNOOPING: binary dump of relay info option, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x1 0x1 0x0 0x0 0x2 0x8 0x0 0x6 0x4C 0x5D 0x3C 0xEB 0x43 0x40
*Dec 6 22:42:19.579: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 6 22:42:19.579: DHCP_SNOOPING: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (250)
*Dec 6 22:42:19.579: DHCP_SNOOPING: L2RELAY: cannot find default gw for bd 250: src intf TwentyFiveGigE1/0/1
Nota: Il messaggio di debug finale indica che il dispositivo non è stato in grado di identificare il gateway predefinito per la VLAN 250.
Verifica Leaf-02
Poiché Leaf-2 è la foglia del bordo attivo all'interno del fabric VxLAN, è responsabile dell'inoltro delle informazioni correlate al gateway predefinito.
Passaggio 1. Procedere per convalidare la funzionalità di L2VPN EVPN per annunciare il gateway predefinito.
Leaf-2#show l2vpn evpn summary
L2VPN EVPN
EVPN Instances (excluding point-to-point): 1
VLAN Based: 1
Vlans: 1
BGP: ASN 65000, address-family l2vpn evpn configured
Router ID: 203.0.113.2
Global Replication Type: Ingress
ARP/ND Flooding Suppression: Enabled
Connectivity to Core: UP
MAC Duplication: seconds 180 limit 5
MAC Addresses: 5
Local: 3
Remote: 2
Duplicate: 0
IP Duplication: seconds 180 limit 5
IP Addresses: 2
Local: 2
Remote: 0
Duplicate: 0
Advertise Default Gateway: No
Default Gateway Addresses: 0
Local: 0
Remote: 0
Maximum number of Route Targets per EAD-ES route: 200
Multi-home aliasing: Enabled
Multi-home send proxy MAC/IP: Enabled
Multi-home device ID: 0000.5e00.0101
Global IP Local Learn: Enabled
IP local learning limits
IPv4: 4 addresses per-MAC
IPv6: 12 addresses per-MAC
IP local learning timers
Down: 10 minutes
Poll: 1 minutes
Reachable: 5 minutes
Stale: 30 minutes
Auto route-target: vni-based
Advertise Multicast: No
Global Anycast Gateway MAC: No
Passaggio 2. L'output precedente convalida che Leaf-2 non stia pubblicizzando il Default-Gateway verso l'altro Leaf-1 all'interno dello stesso fabric VxLAN. Procedere con la configurazione necessaria per eseguire l'annuncio corretto.
Leaf-2(config)#l2vpn evpn
Leaf-2(config-evpn)#default-gateway advertise
Passaggio 3. Dopo aver aggiunto la configurazione, è necessario abilitare la funzionalità EVPN L2VPN.
Leaf-2#show l2vpn evpn summary
--snip--
Advertise Default Gateway: Yes
Passaggio 4. Dopo aver abilitato la funzione, configurare l'annuncio appropriato per il gateway predefinito sull'altra foglia all'interno del fabric VxLAN.
Soluzione del problema 1
La configurazione dell'VPN L2VPN e dello snooping DHCP funziona come previsto. Tuttavia, l'annuncio gateway predefinito non viene eseguito. Pertanto, i dispositivi terminali connessi a Leaf-1 non possono ricevere un indirizzo IP dal server DHCP.
Per risolvere il problema, è necessario configurare l'annuncio.
Passaggio 1. Configurare un ACL e una mappa dei percorsi per annunciare il gateway predefinito tramite BGP agli altri dispositivi foglia della rete.
Leaf-2(config)#ip access-list extended GW250
Leaf-2(config-ext-nacl)#10 permit ip host 192.0.2.254 any (permit the IP address if the GW)
Leaf-2(config)#route-map CGW
Leaf-2(config-route-map)#match ip address GW250
Leaf-2(config-route-map)#match evpn route-type 2-mac-ip
Leaf-2(config-route-map)#set extcommunity default-gw
Leaf-2(config)#router bgp 65000
Leaf-2(config-router)#address-family l2vpn evpn
Leaf-2(config-router-af)#neighbor 203.0.113.3 route-map CGW out
Passaggio 2. Dopo aver aggiunto la configurazione precedente, verificare Leaf-1 per visualizzare l'annuncio del gateway predefinito corretto.
Leaf-1#show l2vpn evpn default-gateway
Valid Default Gateway Address EVI VLAN MAC Address Source
----- --------------------------------------- ----- ----- -------------- -----------
Y 192.0.2.254 250 250 3473.2db8.bee3 203.0.113.2
Nota: Sul VTEP Bordo, la verifica del gateway predefinito visualizza un valore vuoto. Questo è il comportamento previsto, in quanto il gateway centralizzato è collegato direttamente al VTEP di confine.
Leaf-2#show l2vpn evpn default-gateway
Valid Default Gateway Address EVI VLAN MAC Address Source
----- --------------------------------------- ----- ----- -------------- -----------
Ora i dispositivi Leaf mostrano correttamente l'annuncio del gateway predefinito. Verificare che i dispositivi terminali ricevano correttamente l'indirizzo IP da DHCP.
Verifica host 1
Passaggio 1. Sull'host 1, richiedere un indirizzo IP tramite DHCP:
Host1#show running-config interface vlan 250
Building configuration...
Current configuration : 42 bytes
!
interface Vlan250
ip address dhcp
end
Passaggio 2. Verificare che l'indirizzo IP sia stato assegnato correttamente:
Host1#show ip interface brief | include DHCP
Vlan250 unassigned YES DHCP up up
Passaggio 3. Se l'indirizzo IP non è assegnato correttamente dopo che il gateway predefinito è stato annunciato correttamente dal Border Leaf, procedere con la risoluzione dei problemi DHCP.
Verifica Foglia 2
Passaggio 1. Abilitare il debug per DHCP, in particolare per lo snooping DHCP, per osservare come il dispositivo elabora i pacchetti quando li inoltra all'esterno dell'infrastruttura VXLAN.
Leaf-2#debug ip dhcp snooping packet
DHCP Snooping Packet debugging is on
Passaggio 2. Riavviare il processo DHCP sul dispositivo host e rivedere i registri:
Leaf-2#debug ip dhcp snooping packet
*Dec 12 20:11:43.891: DHCP_SNOOPING: received new DHCP packet from input interface (Tunnel0)
*Dec 12 20:11:43.891: DHCP Memory dump is printed for process packet
<snip>
*Dec 12 20:11:43.902: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Tu0, MAC da: 3473.2db8.bee3, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 20:11:43.902: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 12 20:11:43.902: DHCP_SNOOPING: bridge packet output port set is null, packet is dropped.
Passaggio 3. I registri precedenti indicano che il pacchetto viene scartato. Questo messaggio indica che la funzionalità di snooping DHCP sullo switch ha ricevuto un pacchetto DHCP che non può essere inoltrato perché la porta di output non è valida. Questo si verifica in genere quando lo snooping DHCP non è in grado di determinare la porta di uscita appropriata per l'inoltro del pacchetto DHCP.
Passaggio 4. Per risolvere questo problema, l'interfaccia che punta al gateway centralizzato deve essere configurata come attendibile.
Leaf-2(config)#interface fortyGigabitEthernet 2/0/1
Leaf-2(config-if)#ip dhcp snooping trust
Passaggio 5. Verificare se l'assegnazione dell'indirizzo IP tramite DHCP funziona come previsto.
Leaf-2#debug ip dhcp snooping packet
*Dec 12 20:33:54.156: DHCP Memory dump is printed for process packet
<snip>
*Dec 12 20:33:54.167: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Tu0, MAC da: 3473.2db8.bee3, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 20:33:54.167: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 12 20:33:54.167: DHCP_SNOOPING: bridge packet send packet to port: FortyGigabitEthernet2/0/1, pak_vlan 250.
Passaggio 6. L'evidenza indica che il dispositivo ora identifica correttamente l'interfaccia fisica tramite il pacchetto DHCP DISCOVER e deve essere inoltrata perché l'interfaccia è contrassegnata come attendibile dalla prospettiva dello snooping DHCP. Tuttavia, l'assegnazione dell'indirizzo IP non funziona ancora come previsto.
Verifica gateway centralizzata
Passaggio 1. Ora che il Border Leaf inoltra i pacchetti DHCP tramite l'interfaccia appropriata, se l'assegnazione dell'indirizzo IP continua a non riuscire, procedere con le procedure standard di risoluzione dei problemi DHCP.
Centralized-Gateway#debug ip dhcp server packet
DHCP server packet debugging is on.
*Dec 12 20:39:36.029: DHCPD: tableid for 192.0.2.254 on Vlan250 is 0
*Dec 12 20:39:36.029: DHCPD: client's VPN is .
*Dec 12 20:39:36.029: DHCPD: No option 125
*Dec 12 20:39:36.029: DHCPD: Option 124: Vendor Class Information
*Dec 12 20:39:36.029: DHCPD: Enterprise ID: 9
*Dec 12 20:39:36.029: DHCPD: Vendor-class-data-len: 13
*Dec 12 20:39:36.029: DHCPD: Data: 43393330304C2D3234502D3447
*Dec 12 20:39:36.029: DHCPD: inconsistent relay information.
*Dec 12 20:39:36.029: DHCPD: relay information option exists, but giaddr is zero
Passaggio 2. In base all'output del comando debug del gateway centralizzato e ai risultati dell'acquisizione dei pacchetti, è necessaria un'ulteriore configurazione per evitare che il dispositivo ignori i pacchetti quando il campo giaddr è impostato su zero.
Quando si riceve un pacchetto DHCP con l'opzione Relay Information presente ma l'indirizzo IP del gateway (giaddr) è impostato su tutti gli zeri, l'agente di inoltro DHCP, per impostazione predefinita, scarta il pacchetto. Per risolvere questo problema, configurare il comando ip dhcp relay information trusted.
Passaggio 3. Per verificare che il dispositivo riceva il pacchetto, eseguire un'acquisizione del pacchetto:
Configure an Access-list to filter the interested traffic.
Extended IP access list dhcp
10 permit udp any any eq 67
20 permit udp any eq 67 any
Configure the capture.
Centralized-Gateway#monitor capture tac interface gigabitethernet1/0/1 both access-list dhcp buffer size 10
Centralized-Gateway#monitor capture cap start
Started capture point : cap
Centralized-Gateway#monitor capture cap stop
Capture statistics collected at software:
Capture duration - 58 seconds
Packets received - 6
Packets dropped - 0
Packets oversized - 0
Bytes dropped in asic - 0
Centralized-Gateway#show monitor capture cap buffer display-filter "eth.addr==10:b3:d6:8b:3b:e3" detailed
Starting the packet display ........ Press Ctrl + Shift + 6 to exit
Frame 1: 397 bytes on wire (3176 bits), 397 bytes captured (3176 bits) on interface /tmp/epc_ws/wif_to_ts_pipe, id 0
Interface id: 0 (/tmp/epc_ws/wif_to_ts_pipe)
Interface name: /tmp/epc_ws/wif_to_ts_pipe
Encapsulation type: Ethernet (1)
Arrival Time: Dec 12, 2025 18:35:21.821468000 UTC
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1765564521.821468000 seconds
[Time delta from previous captured frame: 0.000000000 seconds]
[Time delta from previous displayed frame: 0.000000000 seconds]
[Time since reference or first frame: 0.000000000 seconds]
Frame Number: 1
Frame Length: 397 bytes (3176 bits)
Capture Length: 397 bytes (3176 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ethertype:vlan:ethertype:ip:udp:dhcp]
Ethernet II, Src: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3), Dst: 34:73:2d:b8:be:e3 (34:73:2d:b8:be:e3)
Destination: 34:73:2d:b8:be:e3 (34:73:2d:b8:be:e3)
Address: 34:73:2d:b8:be:e3 (34:73:2d:b8:be:e3)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 250
000. .... .... .... = Priority: Best Effort (default) (0)
...0 .... .... .... = DEI: Ineligible
.... 0000 1111 1010 = ID: 250
Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 0.0.0.0, Dst: 255.255.255.255
0100 .... = Version: 4
.... 0101 = Header Length: 20 bytes (5)
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
0000 00.. = Differentiated Services Codepoint: Default (0)
.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
Total Length: 379
Identification: 0x4b04 (19204)
Flags: 0x00
0... .... = Reserved bit: Not set
.0.. .... = Don't fragment: Not set
..0. .... = More fragments: Not set
Fragment Offset: 0
Time to Live: 255
Protocol: UDP (17)
Header Checksum: 0x6f6e [validation disabled]
[Header checksum status: Unverified]
Source Address: 0.0.0.0
Destination Address: 255.255.255.255
User Datagram Protocol, Src Port: 68, Dst Port: 67
Source Port: 68
Destination Port: 67
Length: 359
Checksum: 0x2ae5 [unverified]
[Checksum Status: Unverified]
[Stream index: 0]
[Timestamps]
[Time since first frame: 0.000000000 seconds]
[Time since previous frame: 0.000000000 seconds]
UDP payload (351 bytes)
Dynamic Host Configuration Protocol (Discover)
Message type: Boot Request (1)
Hardware type: Ethernet (0x01)
Hardware address length: 6
Hops: 0
Transaction ID: 0xe9986585
Seconds elapsed: 0
Bootp flags: 0x8000, Broadcast flag (Broadcast)
1... .... .... .... = Broadcast flag: Broadcast
.000 0000 0000 0000 = Reserved flags: 0x0000
Client IP address: 0.0.0.0
Your (client) IP address: 0.0.0.0
Next server IP address: 0.0.0.0
Relay agent IP address: 0.0.0.0
Client MAC address: 10:b3:d6:8b:3b:e3 (10:b3:d6:8b:3b:e3)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Option: (53) DHCP Message Type (Discover)
Length: 1
DHCP: Discover (1)
Option: (57) Maximum DHCP Message Size
Length: 2
Maximum DHCP Message Size: 1200
Option: (61) Client identifier
Length: 27
Type: 0
Client Identifier: cisco-10b3.d68b.3be3-Vl250
Passaggio 4. In base all'acquisizione precedente, il pacchetto DHCP viene ricevuto correttamente dal dispositivo.
Soluzione del problema 2
Passaggio 1. In base all'output del comando debug del gateway centralizzato e ai risultati dell'acquisizione dei pacchetti, è necessaria un'ulteriore configurazione per evitare che il dispositivo ignori i pacchetti quando il campo giaddr è impostato su zero.
Quando si riceve un pacchetto DHCP con l'opzione Relay Information presente, ma l'indirizzo IP del gateway (giaddr) è impostato su tutti gli zeri, l'agente di inoltro DHCP in genere scarta il pacchetto.
Per risolvere questo problema, configurare il comando ip dhcp relay information trusted.
Centralized-Gateway(config)#interface vlan 250
Centralized-Gateway(config-if)#ip dhcp relay information trusted
Passaggio 2. Procedere con la verifica richiedendo un indirizzo IP all'host 1.
Host1#
*Dec 12 21:32:12.659: %DHCP-6-ADDRESS_ASSIGN: Interface Vlan250 assigned DHCP address 192.0.2.1, mask 255.255.255.0, hostname Host1
Leaf-2#
*Dec 12 21:36:03.232: DHCP_SNOOPING: received new DHCP packet from input interface (Tunnel0)
<snip>
*Dec 12 21:36:03.243: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Tu0, MAC da: 3473.2db8.bee3, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 21:36:03.243: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 12 21:36:03.243: DHCP_SNOOPING: bridge packet send packet to port: FortyGigabitEthernet2/0/1, pak_vlan 250.
*Dec 12 21:36:03.245: DHCP_SNOOPING: received new DHCP packet from input interface (FortyGigabitEthernet2/0/1)
<snip>
*Dec 12 21:36:03.255: DHCP_SNOOPING: process new DHCP packet, message type: DHCPOFFER, input interface: Fo2/0/1, MAC da: ffff.ffff.ffff, MAC sa: 3473.2db8.bee3, IP da: 255.255.255.255, IP sa: 192.0.2.254, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 192.0.2.1, DHCP siaddr: 0.0.0.0, DHCP giaddr: 192.0.2.254, DHCP chaddr: 10b3.d68b.3be3, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 21:36:03.255: DHCP_SNOOPING: binary dump of option 82, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x1 0x1 0x0 0x0 0x2 0x8 0x0 0x6 0x4C 0x5D 0x3C 0xEB 0x43 0x40
*Dec 12 21:36:03.256: DHCP_SNOOPING: binary dump of extracted circuit id, length: 14 data:
0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x1 0x1 0x0 0x0
*Dec 12 21:36:03.256: DHCP_SNOOPING: binary dump of extracted remote id, length: 10 data:
0x2 0x8 0x0 0x6 0x4C 0x5D 0x3C 0xEB 0x43 0x40
*Dec 12 21:36:03.256: actual_fmt_cid OPT82_FMT_CID_VXLAN_MOD_PORT_INTF global_opt82_fmt_rid OPT82_FMT_RID_DEFAULT_GLOBAL global_opt82_fmt_cid OPT82_FMT_CID_DEFAULT_GLOBAL cid: sub_option_length 12
*Dec 12 21:36:03.256: dhcp_snooping_platform_is_local_dhcp_packet: VXLAN-MOD-PORT opt82 vni 10250, vlan_id 250
*Dec 12 21:36:03.256: DHCP_SNOOPING: opt82 data indicates not a local packet
*Dec 12 21:36:03.256: DHCP_SNOOPING: EVPN enabled Ex GW:fabric relay can't parse option 82 data of the message,it is either in wrong format or not inserted by local switch
*Dec 12 21:36:03.256: DHCP_SNOOPING: client address lookup failed to locate client interface, retry lookup using packet mac DA: ffff.ffff.ffff
*Dec 12 21:36:03.256: DHCP_SNOOPING: lookup packet destination port failed to get mat entry for mac: 10b3.d68b.3be3 vlan_id 250
*Dec 12 21:36:03.256: DHCP_SNOOPING: L2RELAY: Ex GW unicast bridge packet to fabric: vlan id 250 from Fo2/0/1
<snip>
*Dec 12 21:36:03.401: DHCP_SNOOPING: process new DHCP packet, message type: DHCPREQUEST, input interface: Tu0, MAC da: 3473.2db8.bee3, MAC sa: 10b3.d68b.3be3, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.3be3, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 21:36:03.401: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 12 21:36:03.401: DHCP_SNOOPING: bridge packet send packet to port: FortyGigabitEthernet2/0/1, pak_vlan 250.
*Dec 12 21:36:03.402: DHCP_SNOOPING: received new DHCP packet from input interface (FortyGigabitEthernet2/0/1)
<snip>
*Dec 12 21:36:03.413: DHCP_SNOOPING: process new DHCP packet, message type: DHCPACK, input interface: Fo2/0/1, MAC da: ffff.ffff.ffff, MAC sa: 3473.2db8.bee3, IP da: 255.255.255.255, IP sa: 192.0.2.254, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 192.0.2.1, DHCP siaddr: 0.0.0.0, DHCP giaddr: 192.0.2.254, DHCP chaddr: 10b3.d68b.3be3, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 21:36:03.413: DHCP_SNOOPING: binary dump of option 82, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x1 0x1 0x0 0x0 0x2 0x8 0x0 0x6 0x4C 0x5D 0x3C 0xEB 0x43 0x40
*Dec 12 21:36:03.413: DHCP_SNOOPING: binary dump of extracted circuit id, length: 14 data:
0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x1 0x1 0x0 0x0
*Dec 12 21:36:03.413: DHCP_SNOOPING: binary dump of extracted remote id, length: 10 data:
0x2 0x8 0x0 0x6 0x4C 0x5D 0x3C 0xEB 0x43 0x40
*Dec 12 21:36:03.413: actual_fmt_cid OPT82_FMT_CID_VXLAN_MOD_PORT_INTF global_opt82_fmt_rid OPT82_FMT_RID_DEFAULT_GLOBAL global_opt82_fmt_cid OPT82_FMT_CID_DEFAULT_GLOBAL cid: sub_option_length 12
*Dec 12 21:36:03.413: dhcp_snooping_platform_is_local_dhcp_packet: VXLAN-MOD-PORT opt82 vni 10250, vlan_id 250
*Dec 12 21:36:03.413: DHCP_SNOOPING: opt82 data indicates not a local packet
*Dec 12 21:36:03.413: DHCP_SNOOPING: EVPN enabled Ex GW:fabric relay can't parse option 82 data of the message,it is either in wrong format or not inserted by local switch
*Dec 12 21:36:03.413: DHCP_SNOOPING: client address lookup failed to locate client interface, retry lookup using packet mac DA: ffff.ffff.ffff
*Dec 12 21:36:03.413: DHCP_SNOOPING: lookup packet destination port failed to get mat entry for mac: 10b3.d68b.3be3 vlan_id 250
*Dec 12 21:36:03.413: DHCP_SNOOPING: can't find client's destination port, packet is assumed to be not from local switch, no binding update is needed.
*Dec 12 21:36:03.413: DHCP_SNOOPING: client address lookup failed to locate client interface, retry lookup using packet mac DA: ffff.ffff.ffff
*Dec 12 21:36:03.413: DHCP_SNOOPING: lookup packet destination port failed to get mat entry for mac: 10b3.d68b.3be3 vlan_id 250
*Dec 12 21:36:03.413: DHCP_SNOOPING: L2RELAY: Ex GW unicast bridge packet to fabric: vlan id 250 from Fo2/0/1
Passaggio 3. L'indirizzo IP è stato assegnato correttamente e si consiglia di convalidare lo stesso comportamento dal punto di vista dell'host 2.
Host2#
*Dec 12 21:13:03.926: %DHCP-6-ADDRESS_ASSIGN: Interface Vlan250 assigned DHCP address 192.0.2.2, mask 255.255.255.0, hostname Host2
Leaf-2#
*Dec 12 22:08:15.417: DHCP_SNOOPING: received new DHCP packet from input interface (FortyGigabitEthernet2/0/2)
<snip>
*Dec 12 22:08:15.428: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Fo2/0/2, MAC da: ffff.ffff.ffff, MAC sa: 10b3.d68b.1963, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.1963, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 22:08:15.428: DHCP_SNOOPING: add relay information option.
*Dec 12 22:08:15.428: DHCP_SNOOPING: Encoding opt82 CID in vlan-mod-port format
*Dec 12 22:08:15.428: DHCP_SNOOPING:VxLAN : vlan_id 250 VNI 10250 mod 2 port 2
*Dec 12 22:08:15.428: DHCP_SNOOPING: Encoding opt82 RID in MAC address format
*Dec 12 22:08:15.428: DHCP_SNOOPING: binary dump of relay info option, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x2 0x2 0x0 0x0 0x2 0x8 0x0 0x6 0x68 0x7D 0xB4 0xA8 0xAF 0x0
*Dec 12 22:08:15.428: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 12 22:08:15.428: DHCP_SNOOPING: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (250)
*Dec 12 22:08:15.428: DHCP_SNOOPING: L2RELAY: cannot find default gw for bd 250: src intf FortyGigabitEthernet2/0/2
*Dec 12 22:08:15.430: DHCP_SNOOPING: received new DHCP packet from input interface (FortyGigabitEthernet2/0/1)
<snip>
*Dec 12 22:08:15.440: DHCP_SNOOPING: process new DHCP packet, message type: DHCPOFFER, input interface: Fo2/0/1, MAC da: ffff.ffff.ffff, MAC sa: 3473.2db8.bee3, IP da: 255.255.255.255, IP sa: 192.0.2.254, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 192.0.2.2, DHCP siaddr: 0.0.0.0, DHCP giaddr: 192.0.2.254, DHCP chaddr: 10b3.d68b.1963, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 22:08:15.440: DHCP_SNOOPING: binary dump of option 82, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x2 0x2 0x0 0x0 0x2 0x8 0x0 0x6 0x68 0x7D 0xB4 0xA8 0xAF 0x0
*Dec 12 22:08:15.440: DHCP_SNOOPING: binary dump of extracted circuit id, length: 14 data:
0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x2 0x2 0x0 0x0
*Dec 12 22:08:15.440: DHCP_SNOOPING: binary dump of extracted remote id, length: 10 data:
0x2 0x8 0x0 0x6 0x68 0x7D 0xB4 0xA8 0xAF 0x0
*Dec 12 22:08:15.440: actual_fmt_cid OPT82_FMT_CID_VXLAN_MOD_PORT_INTF global_opt82_fmt_rid OPT82_FMT_RID_DEFAULT_GLOBAL global_opt82_fmt_cid OPT82_FMT_CID_DEFAULT_GLOBAL cid: sub_option_length 12
*Dec 12 22:08:15.440: dhcp_snooping_platform_is_local_dhcp_packet: VXLAN-MOD-PORT opt82 vni 10250, vlan_id 250
*Dec 12 22:08:15.440: DHCP_SNOOPING: opt82 data indicates local packet
*Dec 12 22:08:15.440: DHCP_SNOOPING: remove relay information option.
*Dec 12 22:08:15.440: DHCP_SNOOPING opt82_fmt_cid_intf OPT82_FMT_CID_VXLAN_MOD_PORT_INTF opt82_fmt_cid_global OPT82_FMT_CID_DEFAULT_GLOBAL cid: sub_option_length 12
*Dec 12 22:08:15.440: DHCP_SNOOPING: VxLAN vlan_id 250 VNI 10250 mod 2 port 2
*Dec 12 22:08:15.440: DHCP_SNOOPING: mod 2 port 2 idb Fo2/0/2 found for 10b3.d68b.1963
*Dec 12 22:08:15.441: DHCP_SNOOPING: calling forward_dhcp_reply
*Dec 12 22:08:15.441: platform lookup dest vlan for input_if: FortyGigabitEthernet2/0/1, is NOT tunnel, if_output: NULL, if_output->vlan_id: 99999, pak->vlan_id: 250
*Dec 12 22:08:15.441: DHCP_SNOOPING opt82_fmt_cid_intf OPT82_FMT_CID_VXLAN_MOD_PORT_INTF opt82_fmt_cid_global OPT82_FMT_CID_DEFAULT_GLOBAL cid: sub_option_length 12
*Dec 12 22:08:15.441: DHCP_SNOOPING: VxLAN vlan_id 250 VNI 10250 mod 2 port 2
*Dec 12 22:08:15.441: DHCP_SNOOPING: mod 2 port 2 idb Fo2/0/2 found for 10b3.d68b.1963
*Dec 12 22:08:15.441: DHCP_SNOOPING: vlan 250 after pvlan check
<snip>
*Dec 12 22:08:15.930: DHCP_SNOOPING: process new DHCP packet, message type: DHCPREQUEST, input interface: Fo2/0/2, MAC da: ffff.ffff.ffff, MAC sa: 10b3.d68b.1963, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 10b3.d68b.1963, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 22:08:15.930: DHCP_SNOOPING: add relay information option.
*Dec 12 22:08:15.930: DHCP_SNOOPING: Encoding opt82 CID in vlan-mod-port format
*Dec 12 22:08:15.930: DHCP_SNOOPING:VxLAN : vlan_id 250 VNI 10250 mod 2 port 2
*Dec 12 22:08:15.930: DHCP_SNOOPING: Encoding opt82 RID in MAC address format
*Dec 12 22:08:15.930: DHCP_SNOOPING: binary dump of relay info option, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x2 0x2 0x0 0x0 0x2 0x8 0x0 0x6 0x68 0x7D 0xB4 0xA8 0xAF 0x0
*Dec 12 22:08:15.930: DHCPS BRIDGE PAK: vlan=250 platform_flags=1
*Dec 12 22:08:15.930: DHCP_SNOOPING: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (250)
*Dec 12 22:08:15.930: DHCP_SNOOPING: L2RELAY: cannot find default gw for bd 250: src intf FortyGigabitEthernet2/0/2
*Dec 12 22:08:15.932: DHCP_SNOOPING: received new DHCP packet from input interface (FortyGigabitEthernet2/0/1)
<snip>
*Dec 12 22:08:15.940: DHCP_SNOOPING: process new DHCP packet, message type: DHCPACK, input interface: Fo2/0/1, MAC da: ffff.ffff.ffff, MAC sa: 3473.2db8.bee3, IP da: 255.255.255.255, IP sa: 192.0.2.254, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 192.0.2.2, DHCP siaddr: 0.0.0.0, DHCP giaddr: 192.0.2.254, DHCP chaddr: 10b3.d68b.1963, efp_id: -2136403878, vlan_id: 250, bootpflag:0x32768(Broadcast)
*Dec 12 22:08:15.943: DHCP_SNOOPING: binary dump of option 82, length: 26 data:
0x52 0x18 0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x2 0x2 0x0 0x0 0x2 0x8 0x0 0x6 0x68 0x7D 0xB4 0xA8 0xAF 0x0
*Dec 12 22:08:15.943: DHCP_SNOOPING: binary dump of extracted circuit id, length: 14 data:
0x1 0xC 0x1 0xA 0x0 0x8 0x0 0x0 0x28 0xA 0x2 0x2 0x0 0x0
<snip>
Cronologia delle revisioni
| Revisione | Data di pubblicazione | Commenti |
|---|---|---|
1.0 |
15-Jun-2026
|
Versione iniziale |
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