[j-nsp] MTU question.. n00b

[Chris Kawchuk]

Hi Josh,

MTU size does not change the distance/bandiwdth metric of the routing
protocol (i.e. IGP's such as RIPv2, OSPF, etc).

MTU is used to calculate the largest packet size that may be transmitted
through an interface.

If the packetsize is greater than the MTU, then the router will fragment
the packet into two.

If the packet had the "do not fragment" bit set (in the IP header of the
packet), then the router discards the packet, and sends back an ICMP
"Datagram Too big" message (ICMP Type 3, code 4) back to the source of
the packet, (i.e. whomever was listed in the "source IP address" field
on the discarded packet).

Hope this helps.

Chris Kawchuk (chrisk at distributel.ca)
Director, Data Telecommunications
Distributel Communications Ltd.



-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net
[mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of josh
Sent: November 27, 2005 7:29 AM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] MTU question.. n00b

sorry if this is the wrong mailing list.

i am wondering does changing the MTU affect routing protocol metric or
its not part of the metric calculation ?

thanks,
--josh