OTV on ASR 1K

aviyoshi10 · ‎01-22-2012

Hi,

i need to deploy otv on ASR 1004on IOS XE Release 3S.

the problem is that my WAN interface must run GRE tunnel with MTU 1400.

the application sending 1500 Byte - so, the GRE interface need to fragment the traffic.

i understand that there is otv restriction: OTV sets the Don’t Fragment (DF) bit in the IP header for all OTV control and data packets so that the core cannot fragment these packets.

is that means it will not work ?

is tere another option ?

please advise,

Avi.

ntst · ‎02-07-2012

Avi, I ran across this and thought of you!

From http://www.cisco.com/en/US/docs/ios-xml/ios/wan_otv/configuration/xe-3s/wan-otv-confg.html

Configure the join interface and all Layer 3 interfaces that face the IP core between the OTV edge devices with the highest maximum transmission unit (MTU) size supported by the IP core. OTV sets the Don't Fragment (DF) bit in the IP header for all OTV control and data packets so that the core cannot fragment these packets.

So, set your MTU to 1400, subtract the GRE overhead (24 bytes MTU 1376) if you haven't accounted for it already.

Aries Fernandes · ‎08-02-2013

Have you got this problem resolved? If not do let me know. To ensure MTU is limited to 1400, on the join-interface you have to configure mtu 1400, as mentioned above.

Also, you need to ensure, OTV fragmentation is enabled with the command: '

otv fragmentation join-interface '

Thanks,

Aries