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Packet Drops on 4500 with IPinIP Tunnel

An IPinIP tunnel is implemented across two catalyst switches as follows:

1. Cat4500_VLAN400 <==> IPinIP <==> Cat3500_VLAN400

2. OSPFv2 across tunnel interface

The following behavior is observed:

3. Failure to complete FULL OSPF adjacency

3.1 Cat3500 side goes into INIT state

3.2 Cat4500 side goes into NULL state (-)

4. Input queue drops observed Tunnel_Interface_Cat4500

ACTION

5. Increased HOLD-QUEUE IN on Tunnel_Interface_Cat4500 to match value on corresponding Physical Interface (2000)

RESULT

6. OSPF Adjacency came back

ISSUE

When we 'stress' tested this link, SUPRISINGLY packet drops and OSPF adjacency loss returned when sending more than 40kbps...this is too low a threshold a Cat4500.

QUESTION

Does the cat4500 significantly de-prioritize Tunnel (IPinIP in this case) processing compared physical interfaces? i.e does the cat4500 process switch IPinIP traffic? Conversely, is there a way to improve IPinIP traffic processing on Cat4500?

Note: Cat4500 is running 12.1(13)EW

regards,

Ranga

1 REPLY
Bronze

Re: Packet Drops on 4500 with IPinIP Tunnel

Catalyst 4500 does not support IPinIP tunnel mode, yet.

Bug is been worked on. Don't know if the bug has been filed yet.

Use GRE. But before you do that, upgrade to 12.1(20)EW.

GRE is broken before that code.

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