管理员希望将防火墙威胁防御(FTD)设备配置为工作站的DHCP服务器,并为终端设备设置DHCP地址保留。
配置包括在防火墙管理中心(FMC)本地配置FTD的DHCP服务器,并使用FlexConfig添加DHCP IP保留。
防火墙威胁防御(FTD)版本10.x。其他软件版本也会受到影响。
防火墙管理中心(FMC)10.x。其他软件版本也会受到影响。
拓扑

特定DHCP环境包括:
DHCP服务器接口为NET200。
DHCP服务器池为192.0.2.10 - 50。
MAC地址为0000.5E00.5301的终端设备。目标是为此终端保留IP地址192.0.2.45。
池192.0.2.10 - 50在FTD接口NET200上配置:

对于DHCP IP地址保留,请使用FlexConfig:
部署类型:设置为“一次”。
配置类型:设置为“Append”(这是默认值)。也可以使用“预置”。

已部署的配置:
device# show run dhcpd
dhcpd address 192.0.2.10-192.0.2.50 NET200
dhcpd enable NET200
dhcpd reserve-address 192.0.2.45 0000.5E00.5301 NET200
要捕获DHCP数据包,请使用以下命令:
device# capture CAPI interface NET200 match udp any any eq bootpc
device# capture CAPI interface NET200 match udp any any eq bootps
DHCP客户端侦听UDP端口68。
DHCP服务器侦听UDP端口67。
DHCP调试:
device# debug dhcpd event 255
debug dhcpd event enabled at level 255
device# debug dhcpd packet 255
debug dhcpd packet enabled at level 255
注意:请谨慎使用调试!
IP地址分配过程中的调试输出:
DHCPD/RA: Server msg received, fip=ANY, fport=0 on NET200 interface
DHCPD: DHCPDISCOVER received from client 0100.5056.885f.d1 on interface NET200.
DHCPD:IP 248.57.222.26 ARP entry removed from the cache
DHCPD: send ping pkt to 192.0.2.45
DHCPD: ping got no response for ip: 192.0.2.45
DHCPD: MAC 0000.5E00.5301 is reserved for IP 192.0.2.45, allocating it
DHCPD: Add binding 192.0.2.45 to radix tree
DHCPD/RA: Binding successfully added to hash table
dhcpd_create_automatic_binding() adding NP rule for client 192.0.2.45
DHCPD: assigned IP address 192.0.2.45 to client 0100.5056.885f.d1.
DHCPD: Sending DHCPOFFER to client 0100.5056.885f.d1 (192.0.2.45).
DHCPD: Total # of raw options copied to outgoing DHCP message is 0.
DHCPD/RA: creating ARP entry (192.0.2.45, 0000.5E00.5301).
DHCPD: unicasting BOOTREPLY to client 0000.5E00.5301(192.0.2.45).
DHCPD/RA: Server msg received, fip=ANY, fport=0 on NET200 interface
DHCPD: DHCPDISCOVER received from client 0100.5056.885f.d1 on interface NET200.
DHCPD: Sending DHCPOFFER to client 0100.5056.885f.d1 (192.0.2.45).
DHCPD: Total # of raw options copied to outgoing DHCP message is 0.
DHCPD/RA: creating ARP entry (192.0.2.45, 0000.5E00.5301).
DHCPD: unicasting BOOTREPLY to client 0000.5E00.5301(192.0.2.45).
DHCPD/RA: Server msg received, fip=ANY, fport=0 on NET200 interface
DHCPD: DHCPDISCOVER received from client 0100.5056.885f.d1 on interface NET200.
DHCPD: Sending DHCPOFFER to client 0100.5056.885f.d1 (192.0.2.45).
DHCPD: Total # of raw options copied to outgoing DHCP message is 0.
DHCPD/RA: creating ARP entry (192.0.2.45, 0000.5E00.5301).
DHCPD: unicasting BOOTREPLY to client 0000.5E00.5301(192.0.2.45).
DHCPD/RA: Server msg received, fip=ANY, fport=0 on NET200 interface
DHCPD: DHCPREQUEST received from client 0100.5056.885f.d1.
DHCPD: Extracting client address from the message
DHCPD: State = DHCPS_REBOOTING
DHCPD: State = DHCPS_REQUESTING
DHCPD: Client 0100.5056.885f.d1 specified it's address 192.0.2.45
DHCPD: Client is on the correct network
DHCPD: Client accepted our offer
DHCPD: Client and server agree on address 192.0.2.45
DHCPD: Renewing client 0100.5056.885f.d1 lease
DHCPD: Client lease can be renewed
DHCPD: Sending DHCPACK to client 0100.5056.885f.d1 (192.0.2.45).
DHCPD: Including FQDN option name 'DESKTOP-VQ7968K' rcode1=0, rcode2=0 flags=0x0
DHCPD: Total # of raw options copied to outgoing DHCP message is 0.
DHCPD/RA: creating ARP entry (192.0.2.45, 0000.5E00.5301).
DHCPD: unicasting BOOTREPLY to client 0000.5E00.5301(192.0.2.45).
DHCP绑定的验证:
device# show dhcpd binding
IP address Client Identifier Lease expiration Type
192.0.2.45 0100.005e.0053.01 3589 seconds Automatic
FMC本身不支持DHCP IP地址预留的配置。因此,必须使用FlexConfig来配置IP地址保留。
相关增强缺陷:思科漏洞ID CSCwn24229。
| 版本 | 发布日期 | 备注 |
|---|---|---|
1.0 |
14-May-2026
|
初始版本 |