About jakelomax

jakelomax · 02-12-2013

I have a problem with a router not sending out ICMP unreachables when it receives a frame which exceeds the MTU and the do not fragment flag is set.Cisco IOS Software, s2t54 Software (s2t54-IPSERVICESK9-M), Version 15.0(1)SY2, RELEASE SOFTWARE (fc4)M...

jakelomax · 02-15-2013

Hi Paul, Unfortunately I tried that day one, and the behavior in this version of IOS is to not display that command in the config. The command tunnel path-mtu-discovery effectively enables MTU negotiation so the interface always should have the corre...

jakelomax · 02-14-2013

Here you go Peter, obviously the IP addresses are invalid. Quite simple really.

jakelomax · 02-13-2013

Hi Peter, I'm not sure you understood correctly at all? I'm trying to send a packet that is too large for the MTU on a tunnel, and I'm expecting to get an ICMP unreachable (type 3, code 4) back, but this is not happening and the packets are dropped e...

jakelomax · 02-13-2013

For clarity I should also mention I've captured the packets in/out of the router and don't see any unreachables being sent when I send frames too large for the MTU on the link with the DF flag set.

jakelomax · 02-13-2013

Hi Peter, Thanks for your input. I have already tried that and got a similar response - ie, it looks like they are not sent by the router.

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ICMP unreachables not sent when Fragmentation required, and DF flag set (Type 3, code 4 ICMP message)

ICMP unreachables not sent when Fragmentation required, and DF f

ICMP unreachables not sent when Fragmentation required, and DF f

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