Hey Muhammad, If you set the MTU size to 1520 and set the DF (do not fragment bit) then it will tell all device to never fragment the packets... So if a single hope in the chain can not support the max size of the packet you are sending it will drop the packet.
Sorry not certain if I missed something here but that seems like a simple enough question and answer?!?! Cheers, Simon -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Muhammad Atif Jauhar Sent: Wednesday, 19 January 2011 12:21 PM To: [email protected] Subject: [c-nsp] Ping test with DF bit and MTU / IP MTU value Hi, I have very basic question related to MTU / IP MTU value and ping test with DF bit *Scenario: * I have one router connected to HUB router with Link leasing from SP * * 1. On spoke side, we have GigaEthernet Interface with MTU value set to 1520 2. On HUB side, that link is terminated on layer-2 switch and from there to router sub-interface with IP MTU value set to 1520. 3. Configurations on both router * a. SPOKE Side* * *interface GigabitEthernet0/1 mtu 1520 bandwidth 10000 ip address 192.168.0.1 255.255.255.252 ip ospf network point-to-point ip ospf cost 1000 ip ospf hello-interval 1 ip ospf dead-interval 3 ip ospf mtu-ignore duplex auto speed auto mpls ip *b. HUB Side* * interface GigabitEthernet0/1.100 bandwidth 10000 encapsulation dot1Q 100 ip address 192.168.0.2 255.255.255.252 ip mtu 1520 ip ospf network point-to-point ip ospf cost 1000 ip ospf hello-interval 1 ip ospf dead-interval 3 ip ospf mtu-ignore mpls ip * *Issue:* I am testing the link and face issue. 1. while performing ping test without df bit, I am able to ping with size upto 18024 2. while performing ping test with df bit, I am able to ping with size 1520 3. while performing ping test with df bit, I am able to ping with size more than 1520 *Kindly let me know, why I am not able to ping with DF bit with size more than 1520 (MTU value). How can I troubleshoot the issue. * * * *Any comment please* -- Regards, Muhammad Atif Jauhar (+60-10-2155076) _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ Buy your loved one the gift of peace of mind with an RACQ gift membership. Join the Club today at www.racq.com/membership, 13 1905, 24 hours every day or in store Please Note: If you are not the intended recipient, please delete this email as its use is prohibited. RACQ does not warrant or represent that this email is free from viruses or defects. If you do not wish to receive any further commercial electronic messages from RACQ please e-mail [email protected] or contact RACQ on 13 19 05. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
