ip tcp path-mtu-discovery vs neighbor A.B.C.D transport path-mtu-discovery

[rathinilesh]

Hi,

Does enabling or disabling "ip tcp path-mtu-discovery" globally affect the bgp neighbor "path-mtu-discovery" by any way ?

The doc cd says as below

To enable the Path MTU Discovery feature for all new TCP connections from the router, use the ip tcp path-mtu-discovery global configuration command

http://www.cisco.com/en/US/docs/ios/12_2/ipaddr/command/reference/1rfip2.html#wp1101164

To enable a TCP transport session option for a Border Gateway Protocol (BGP) session, use the neighbor transport command in router or address family configuration mode.

path-mtu-discovery Enables TCP transport path maximum transmission unit (MTU) discovery. TCP path MTU discovery is enabled by default.

http://http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp4.html#wp1144431

Regards,

Nilesh

[Alessio Andreoli]

Hi nilesh,

they are unrelated because the different layer they need to work with (MTU layer 2 vs TCP layer 4) however, you need to pay attention to let these to values to work together to avoid excessive fragmentation or retransmissions due to a too big segment vs some limits to the MTU.

Although they should not have impact on BGP, i would enable neighbor transport only with an outage of at least 30 minutes planned. Never challenging BGP

HTH

Alessio