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Tuesday 30 June 2015

OSPF generates 'interface config error - BAD PACKET' messages

Products
S-Series
Matrix N-Series DFE
K-Series 

Changes
The OSPF routing protocol has been configured on this device, and other OSPF routers exist on the local network. 

Symptoms
An OSPF-originated "BAD PACKET" error message is being syslogged ('show support') every 10 seconds; for example;
<164>Nov 29 07:54:29 10.26.189.11 OSPF[2]Router global: OSPF: Packet dropped - interface config error - src ip 10.26.167.1 - BAD PACKET 

Cause
This is usually caused by a misconfiguration between OSPF routers on common links, though the specific nature of the misconfiguration can vary. 

Solution
Use the "Debug IP/Packet" function (14661) to determine the ingress port(s) of these packets. Once the ingress port is discovered, go to any adjacent peer routers and compare configurations. 

In the example below you can see that the 10.26.167.1-sourced packet is ingressing ethernet port ge.3.48 on vlan 500.
ip access-list standard 1
permit 10.26.167.1 0.0.0.0
exit
 
debug packet filter access-list 1
 
<165>Nov 29 07:54:28 10.26.189.11 DbgIpPkt[3][1] [RECEIVE] in vr global,
on ge.3.48, vlan 500, Matched acl 1, rule[1: permit host 10.26.167.1],
  FATE: Forwarding discontinued, cause: SENT_TO_HOST, out multiple ports
excluding source, vlan.0.500, vr global, nexthop 224.0.0.5, flow
disallowed,
  PKT: InPort(ge.3.48) LEN(82) DA(01:00:5E:00:00:05)
SA(00:1F:45:5B:F4:C1) ETYPE(0800) SIP(10.26.167.1) DIP(224.0.0.5) VER(4)
HLEN(5) TOTALLEN(64) PROTO(89) TOS(192) TTL(1)
<165>Nov 29 07:54:38 10.26.189.11 DbgIpPkt[3][2] [RECEIVE] in vr global,
on ge.3.48, vlan 500, Matched acl 1, rule[1: permit host 10.26.167.1],
  FATE: Forwarding discontinued, cause: SENT_TO_HOST, out multiple ports
excluding source, vlan.0.500, vr global, nexthop 224.0.0.5, flow
disallowed,
  PKT: InPort(ge.3.48) LEN(82) DA(01:00:5E:00:00:05)
SA(00:1F:45:5B:F4:C1) ETYPE(0800) SIP(10.26.167.1) DIP(224.0.0.5) VER(4)
HLEN(5) TOTALLEN(64) PROTO(89) TOS(192) TTL(1)

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