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Dynamic ARP timeout on ASR 1001

Hey all,

Having a bit of an issue with bridge-domains on ASR 1001 and dynamic ARP entries.

Looking through the packet captures, I see the following events

  • DHCP request from CPE
  • DHCP ACK and assignment from DHCP server to CPE
  • Gratuitous ARP sent from CPE.
  • Packets flow as normal.
  • Something triggers dynamic ARP entry to timeout on the BNG (Cisco ASR 1001).
    • a.       Suspect this may be triggered by the DHCP Request renew or the following gratuitous ARP received.
    • See the debug message on the ASR:

*Oct 15 18:18:29.376: IP ARP: rcvd rep src 10.0.30.11 5475.d0df.7f48, dst 10.0.30.11 BDI100

*Oct 15 18:18:29.376: ARP DB: ARP entry of key 10.0.30.11 found

*Oct 15 18:18:29.376: ARP TABLE: modifying entry 10.0.30.11/5475.d0df.7f48 on BD100 for Dynamic

*Oct 15 18:18:29.376: ARP DYNAMIC[N]: Dynamic timeout occurredtimeout = 14400000, refresh_token = 2,refresh_timeout = 60000

*Oct 15 18:18:29.376: ARP DB: ARP entry of key 10.0.30.11 found

  • DHCP client on the CPE eventually sends through a DHCP request for the IP 10.0.30.11.
  • DHCP server replies with ACK.
  • Gratuitous ARP sent from CPE.
  • Dynamic ARP entry is populated.
  • Packets flow as normal.

If I attempt to ping manually from the CPE, the dynamic arp entry is restored on the ASR.

Further details:

               Platform: ASR 1001

                Software: 3.10a (asr1001-universalk9.03.10.00a.S.153-3.S0a-ext.bin)

               Interfaces:

                interface Port-channel2

description Uplink - <redacted>

mtu 2000

ip dhcp relay information option-insert

ip dhcp relay information check-reply none

no ip address

no ip unreachables

no negotiation auto

lacp fast-switchover

lacp max-bundle 1

service instance 1101 ethernet

  encapsulation dot1q 80 second-dot1q 1101

  rewrite ingress tag pop 2 symmetric

  ip dhcp relay information option subscriber-id GCC-CPE-1-1

  service-policy output pm_BNG-WAN-wVoice-Out-12Mbps

  bridge-domain 100

!

service instance 1102 ethernet

  encapsulation dot1q 80 second-dot1q 1102

  rewrite ingress tag pop 2 symmetric

  ip dhcp relay information option subscriber-id GCC-CPE-2-1

  service-policy output pm_BNG-WAN-wVoice-Out-25Mbps

  bridge-domain 100

                interface BDI100

ip address 10.0.30.1 255.255.255.0

ip helper-address 2.2.1.2

GCC-BNG-1#sh run | i bridge

bridge-domain 100

bridge-domain 912

bridge irb

  bridge-domain 100

  bridge-domain 100

bridge 100 protocol vlan-bridge

bridge 100 route ip

Any ideas?

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