فهم أستكشاف أخطاء BGP الأساسية وإصلاحها

المقدمة

يصف هذا المستند إجراء إجراء أستكشاف أخطاء بروتوكول العبارة الحدودية (BGP) وإصلاحها وفهم المخرجات الأساسية على Nexus.

المتطلبات الأساسية

المتطلبات

توصي Cisco بأن تكون لديك معرفة بالمواضيع التالية:

• المحولات Nexus
• BGP

المكونات المستخدمة

لا يقتصر هذا المستند على إصدارات برامج ومكونات مادية معينة.

تم إنشاء المعلومات الواردة في هذا المستند من الأجهزة الموجودة في بيئة معملية خاصة. بدأت جميع الأجهزة المُستخدمة في هذا المستند بتكوين ممسوح (افتراضي). إذا كانت شبكتك قيد التشغيل، فتأكد من فهمك للتأثير المحتمل لأي أمر.

معلومات أساسية

BGP هو بروتوكول عبارة خارجية يستخدم في الشبكات واسعة النطاق لتمكين تبادل معلومات التوجيه والوصول بين الأنظمة الذاتية (ASs). إنه بروتوكول التوجيه الأساسي الذي يشغل نظام التوجيه العالمي للإنترنت.

تحديد التكوين الذي تم تنفيذه لأقران BGP

تحقق من تمكين ميزة BGP على Nexus 9300.

تعريف تكوين عملية BGP وفهمه.

switch# show running-config bgp

!Command: show running-config bgp
!Running configuration last done at: Tue Jul 18 19:45:05 2023
!Time: Tue Jul 18 19:45:44 2023

version 10.2(4) Bios:version 05.47 
feature bgp

router bgp 64512                              -> The AS number of the local BGP speaker.
  router-id 172.17.255.255                    -> BGP speaker identifier. 
  address-family ipv4 unicast                 -> Global address family configuration.
    network 10.100.1.0/24                     -> Specifies a network as local to this autonomous system and adds it to the BGP routing table.
 redistribute direct route-map permit_all     -> Routes redistribution from other routing protocols (OSPF, EIGRP, IS-IS, Static)
 neighbor 10.1.1.1                            -> IP address of the remote BGP peer.
    remote-as 64512                           -> The AS number of the remote BGP peer.*
    address-family ipv4 unicast               -> Local address family configuration.
      prefix-list allow_in in                 -> Prefix-list applied at the inbound of the BGP peer. **
      prefix-list allow_out out               -> Prefix-list applied at the outbound of the BGP peer. **
      soft-reconfiguration inbound always     -> Store the inbound BGP route updates.
  neighbor 172.18.255.255
    remote-as 65535
    update-source loopback10                  -> Interface used to source BGP updates.
    ebgp-multihop 3                           -> Maximum hops to reach peer IP address, it modifies the TTL of the BGP packets 
    address-family ipv4 unicast
      route-map block_route in                -> Route-map applied at the inbound of the BGP peer. **
      route-map no_local out                  -> Route-map applied at the outbound of the BGP peer. **
      soft-reconfiguration inbound always

ملاحظة: يحدد ASN نفسه الذي تم تكوينه على المستوى المحلي والبعيد جلسة عمل iBGP، وتعرف شبكة ASN مختلفة تم تكوينها جلسة عمل eBGP.
          تحتوي خريطة المسار على قيمة تسلسل هيكلي أعلى من قائمة البادئات التي تم تطبيقها على نفس النظير.

كيفية فهم مخرجات بروتوكول بوابة الحدود (BGP) الأساسية

حالة نظير BGP

switch# show ip bgp summary 
BGP summary information for VRF default, address family IPv4 Unicast
BGP router identifier 172.17.255.255, local AS number 64512 -> Local BGP ID and ASN
BGP table version is 67, IPv4 Unicast config peers 2, capable peers 2
20 network entries and 19 paths using 5424 bytes of memory
BGP attribute entries [6/2112], BGP AS path entries [2/20]
BGP community entries [0/0], BGP clusterlist entries [0/0]
13 received paths for inbound soft reconfiguration
12 identical, 0 modified, 1 filtered received paths using 96 bytes

Neighbor       V AS     MsgRcvd   MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.1.1.1       4 64512   346      334     67      0     0 05:25:12 8    -> BGP peer IP address, remote ASN, Time session has been established or down, amount of prefixes received. 
172.18.255.255 4 65535   334      327     67      0     0 05:18:00 8

ملاحظة: يعرض القسم أعلى/أسفل الوقت الذي تكون فيه جلسة عمل نظير BGP أعلى أو أسفل.
          يعرض قسم الحالة/PfxRcd حالة BGP الجلسة قيد التشغيل حاليا. وهي تعرض عدد البادئات التي تم تعلمها من نظيرتها عند تأسيس الحالة.

فهم معلومات نظير BGP.

switch# show ip bgp neighbors 10.1.1.1 
BGP neighbor is 10.1.1.1, remote AS 64512, ibgp link, Peer index 3             -> Peer IP address, remote ASN, type of bgp peering.
  BGP version 4, remote router ID 172.16.255.255                               -> BGP version, Peer Router ID
  Neighbor previous state = OpenConfirm                                        -> Previous BGP state
  BGP state = Established, up for 00:05:29                                     -> Current BGP state and amount of time on it
  Neighbor vrf: default                                                        -> VRF used for the peering.
  Peer is directly attached, interface Ethernet1/49                            -> Interface used to source the updates
  Last read 00:00:28, hold time = 180, keepalive interval is 60 seconds        -> Amount of time from last keepalive received and BGP timers (default)
  Last written 00:00:28, keepalive timer expiry due 00:00:31                   -> Amount of time from last keepalive sent
  Received 363 messages, 0 notifications, 0 bytes in queue
  Sent 354 messages, 1 notifications, 0(0) bytes in queue
  Enhanced error processing: On
    0 discarded attributes
  Connections established 2, dropped 1                                         -> Counters informing the amount of times the BGP seesion has gone up/down
  Last update recd 00:05:28, Last update sent  = 00:05:28                      -> Timer of the last major bgp table update sent and received. 
   Last reset by us 00:06:21, due to holdtimer expired error                   -> Last reset timer and reset reason.
  Last error length sent: 0
  Reset error value sent: 0
  Reset error sent major: 4 minor: 0
  Notification data sent:
  Last reset by peer never, due to No error
  Last error length received: 0
  Reset error value received 0
  Reset error received major: 0 minor: 0
  Notification data received:

  Neighbor capabilities:
  Dynamic capability: advertised (mp, refresh, gr) received (mp, refresh, gr)
  Dynamic capability (old): advertised received
  Route refresh capability (new): advertised received 
  Route refresh capability (old): advertised received 
  4-Byte AS capability: advertised received 
  Address family IPv4 Unicast: advertised received 
  Graceful Restart capability: advertised received

  Graceful Restart Parameters:
  Address families advertised to peer:
    IPv4 Unicast  
  Address families received from peer:
    IPv4 Unicast  
  Forwarding state preserved by peer for:
  Restart time advertised to peer: 120 seconds
  Stale time for routes advertised by peer: 300 seconds
  Restart time advertised by peer: 120 seconds
  Extended Next Hop Encoding Capability: advertised received
  Receive IPv6 next hop encoding Capability for AF:
    IPv4 Unicast  VPNv4 Unicast  

  Message statistics:
                              Sent               Rcvd
  Opens:                         2                  2  
  Notifications:                 1                  0  
  Updates:                      22                 20  
  Keepalives:                  340                339  
  Route Refresh:                 1                  0  
  Capability:                    2                  2  
  Total:                       354                363  
  Total bytes:                7949               7524  
  Bytes in queue:                0                  0  

  For address family: IPv4 Unicast
  BGP table version 88, neighbor version 88
  8 accepted prefixes (8 paths), consuming 2176 bytes of memory
  0 received prefixes treated as withdrawn
  11 sent prefixes (11 paths)                                                  -> Amount of prefixes advertises to peer.
  Inbound soft reconfiguration allowed(always)
  Third-party Nexthop will not be computed.
  Inbound ip prefix-list configured is allow_in, handle obtained
  Outbound ip prefix-list configured is allow_out, handle obtained
  Last End-of-RIB received 00:00:01 after session start
  Last End-of-RIB sent 00:00:01 after session start
  First convergence 00:00:01 after session start with 11 routes sent

  Local host: 10.1.1.2, Local port: 28262
  Foreign host: 10.1.1.1, Foreign port: 179
  fd = 73

فهم جدول BGP

يعرض هذا الإخراج الحالة، الخطوة التالية، القياس، التفضيل المحلي، الوزن، ومسار كل البادئات التي تم التعرف عليها في جدول BGP.

switch# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 88, Local Router ID is 172.17.255.255
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>r10.1.1.0/30        0.0.0.0                  0        100      32768 ?
*>i10.100.1.0/24      10.1.1.1                          100          0 i
*>i10.100.2.0/24      10.1.1.1                          100          0 i
*>i10.100.3.0/24      10.1.1.1                          150          0 i
*>i10.100.4.0/24      10.1.1.1                 0        100          0 ?
*>i10.100.5.0/24      10.1.1.1                 0        100          0 ?
*>i10.100.6.0/24      10.1.1.1                 0        100          0 ?
*>i10.100.7.0/24      10.1.1.1                 0        100          0 ?
*>i10.100.8.0/24      10.1.1.1                 0        100          0 ?
*>r172.17.255.255/32  0.0.0.0                  0        100      32768 ?
*>e172.30.1.0/24      172.18.255.255           0                     0 65535 ?
*>e172.30.2.0/24      172.18.255.255           0                     0 65535 ?
*>e172.30.3.0/24      172.18.255.255           0                     0 65535 ?
*>e172.30.4.0/24      172.18.255.255           0                     0 65535 ?
*>e172.30.5.0/24      172.18.255.255           0                     0 65535 65534 65533 ?
*>e172.30.6.0/24      172.18.255.255           0                     0 65535 65534 65533 ?
*>e172.30.7.0/24      172.18.255.255           0                     0 65535 65534 65533 ?
*>e172.30.8.0/24      172.18.255.255           0                     0 65535 65534 65533 ?
*>r192.168.1.0/30     0.0.0.0                  0        100      32768 ?

يتم الإعلان عن البادئات لمجاورة BGP معينة.

switch# show ip bgp neighbors 172.18.255.255 advertised-routes

Peer 172.18.255.255 routes for address family IPv4 Unicast:
BGP table version is 88, Local Router ID is 172.17.255.255
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

Network            Next Hop        Metric    LocPrf    Weight Path
*>i10.100.1.0/24   10.1.1.1                  100       0 i
*>i10.100.2.0/24   10.1.1.1                  100       0 i
*>i10.100.3.0/24   10.1.1.1                  150       0 i
*>i10.100.4.0/24   10.1.1.1        0         100       0 ?
*>i10.100.5.0/24   10.1.1.1        0         100       0 ?
*>i10.100.6.0/24   10.1.1.1        0         100       0 ?
*>i10.100.7.0/24   10.1.1.1        0         100       0 ?
*>i10.100.8.0/24   10.1.1.1        0         100       0 ?

البادئات المستلمة من نظير BGP قبل أي عوامل تصفية (قائمة البادئات و/أو خريطة المسار)*

switch# show ip bgp neighbors 172.18.255.255 received-routes

Peer 172.18.255.255 routes for address family IPv4 Unicast:
BGP table version is 88, Local Router ID is 172.17.255.255
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

Network                Next Hop         Metric      LocPrf         Weight Path
* e172.18.255.255/32   172.18.255.255    0                         0 65535 ?
*>e172.30.1.0/24       172.18.255.255    0                         0 65535 ?
*>e172.30.2.0/24       172.18.255.255    0                         0 65535 ?
*>e172.30.3.0/24       172.18.255.255    0                         0 65535 ?
*>e172.30.4.0/24       172.18.255.255    0                         0 65535 ?
*>e172.30.5.0/24       172.18.255.255    0                         0 65535 65534 65533 ?
*>e172.30.6.0/24       172.18.255.255    0                         0 65535 65534 65533 ?
*>e172.30.7.0/24       172.18.255.255    0                         0 65535 65534 65533 ?
*>e172.30.8.0/24       172.18.255.255    0                         0 65535 65534 65533 ?

ملاحظة يجب تكوين إعادة التكوين التلقائي الوارد على المجاور

البادئات المستلمة من نظير BGP بعد عوامل التصفية (بادئة-list و/أو خريطة المسار)

switch# show ip bgp neighbors 172.18.255.255 routes

Peer 172.18.255.255 routes for address family IPv4 Unicast:
BGP table version is 88, Local Router ID is 172.17.255.255
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

Network            Next Hop          Metric     LocPrf      Weight Path
*>e172.30.1.0/24   172.18.255.255    0                      0 65535 ?
*>e172.30.2.0/24   172.18.255.255    0                      0 65535 ?
*>e172.30.3.0/24   172.18.255.255    0                      0 65535 ?
*>e172.30.4.0/24   172.18.255.255    0                      0 65535 ?
*>e172.30.5.0/24   172.18.255.255    0                      0 65535 65534 65533 ?
*>e172.30.6.0/24   172.18.255.255    0                      0 65535 65534 65533 ?
*>e172.30.7.0/24   172.18.255.255    0                      0 65535 65534 65533 ?
*>e172.30.8.0/24   172.18.255.255    0                      0 65535 65534 65533 ?

معلومات تفصيلية المسار لبادئة معينة.

switch# show ip bgp 172.30.6.0
BGP routing table information for VRF default, address family IPv4 Unicast
BGP routing table entry for 172.30.6.0/24, version 28                                          -> Prefix and mask
Paths: (3 available, best #3)                                                                  -> Number of possible paths and which one is selected as best option
Flags: (0x8000001a) (high32 00000000) on xmit-list, is in urib, is best urib route, is in HW

Path type: external, path is valid, not best reason: Router Id, no labeled nexthop
AS-Path: 65535 65534 65533 , path sourced external to AS                                       -> As Path to reach the prefix*
172.20.255.255 (metric 0) from 172.20.255.255 (172.20.255.255)                                 -> Next hop towards the prefix
Origin incomplete, MED 0, localpref 100, weight 0

Path type: external, path is valid, not best reason: newer EBGP path, no labeled nexthop
AS-Path: 65535 65534 65533 , path sourced external to AS
172.19.255.255 (metric 0) from 172.19.255.255 (172.19.255.255)
Origin incomplete, MED 0, localpref 100, weight 0

Advertised path-id 1
Path type: external, path is valid, is best path, no labeled nexthop, in rib                  -> Path selection motive
AS-Path: 65535 65534 65533 , path sourced external to AS
172.18.255.255 (metric 0) from 172.18.255.255 (172.18.255.255)
Origin incomplete, MED 0, localpref 100, weight 0

Path-id 1 advertised to peers:                                                               -> BGP peers were the prefix is advertised
10.1.1.2

ملاحظة: *AS-Path يمثل ASN الذي تم تمريره للوصول إلى الموقع الذي تم فيه إنشاء البادئة.
          **يقرأ AS-Path من اليمين إلى اليسار.

لمراجعة أفضل عملية تحديد مسار في BGP، راجع أفضل تحديد لمسار BGP.

معلومات ذات صلة

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