what means the following errors in debug ip packet output

Answered Question
Jul 30th, 2008

Hi,

what means the following errors in debug ip packet output:

Mar 1 00:16:34.419: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 330, rcvd 2

*Mar 1 00:16:34.419: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 330, stop pr

ocess pak for forus packet

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16, len 330, local f

eature, Redirection Cli(6), rtype 0, forus FALSE, sendself FALSE, mtu 0

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16, len 330, local f

eature, Clustering(7), rtype 0, forus FALSE, sendself FALSE, mtu 0

*Mar 1 00:16:34.419: IP: tableid=0, s=10.132.16.1 (local), d=10.132.1.16 (Vlan1

0), routed via FIB

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16 (Vlan10), len 330

, sending

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16 (Vlan10), len 330

, output feature, Check hwidb(63), rtype 1, forus FALSE, sendself FALSE, mtu 0

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16 (Vlan10), len 330

, sending full packet

Thank you

Roman

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Correct Answer by Giuseppe Larosa about 8 years 5 months ago

Hello Roman,

I suppose you are using a multilayer switch.

I tried to look at command reference for debug ip packet in 12.2SX used in Cat6500.

I didn't find forus packet.

However, the first raw should be a DHCP request from a booting client if no ip helper-address pointing to a dhcp server is configured under vlan1 SVI the packet is discarded for its broadcast destination and this is correct behavior

the following lines are about a packet with source 10.132.16.1 with d= 10.132.1.16 and same size 330 byte as first discarded packet.

This packet is sent to 10.132.1.16.

I may be wrong but I think that you have ip helper-address under vlan1 pointing to ip 10.132.1.16 and that vlan1's ip address is 10.132.16.1

If so you are seeing the switch activity when receiving a dhcp request :

original packet is discarded

a modified version as per ip helper-address is routed to vlan10:

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16 (Vlan10), len 330

, sending full packet

Hope to help

Giuseppe

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Correct Answer
Giuseppe Larosa Wed, 07/30/2008 - 09:10

Hello Roman,

I suppose you are using a multilayer switch.

I tried to look at command reference for debug ip packet in 12.2SX used in Cat6500.

I didn't find forus packet.

However, the first raw should be a DHCP request from a booting client if no ip helper-address pointing to a dhcp server is configured under vlan1 SVI the packet is discarded for its broadcast destination and this is correct behavior

the following lines are about a packet with source 10.132.16.1 with d= 10.132.1.16 and same size 330 byte as first discarded packet.

This packet is sent to 10.132.1.16.

I may be wrong but I think that you have ip helper-address under vlan1 pointing to ip 10.132.1.16 and that vlan1's ip address is 10.132.16.1

If so you are seeing the switch activity when receiving a dhcp request :

original packet is discarded

a modified version as per ip helper-address is routed to vlan10:

*Mar 1 00:16:34.419: IP: s=10.132.16.1 (local), d=10.132.1.16 (Vlan10), len 330

, sending full packet

Hope to help

Giuseppe

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