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Cisco Bug: CSCtc31711 - PMTUD sets Path destination to MTU 62, expire never

Last Modified

Feb 22, 2014

Products (1)

  • Cisco IOS

Known Affected Releases

12.4(18b)

Description (partial)

Symptom:
Path MTU calculated at MTU 62.  Certain host applications with DF-Bit were then unable to send traffic over the Tunnel.

To illustrate when broken:

show interface tunne0l:
<snip>
Path destination 192.168.1.1: MTU 62, expires never when broken


After a shut/no shut of the tunnel interface traffic with DF-Bit set flows once again.

show interface tunne0l:
<snip>
Path destination 192.168.1.1: MTU 0, expires never


Conditions:
Both local and remote routers were running 12.4(18a)
tunnel path-mtu-discovery set on local peer only.

Local router started PMTUD while the link on the remote peer router was down but before routing converged on the locall router.
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