tag:blogger.com,1999:blog-8872651374870949504.post6858147532371360947..comments2024-02-15T12:24:29.279+05:30Comments on Nagendra's Blog: BGP Path MTU DiscoveryNagendra Kumarhttp://www.blogger.com/profile/06536056072014454129noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-8872651374870949504.post-79539619103282130992023-10-30T20:06:30.199+05:302023-10-30T20:06:30.199+05:30Thank you for the comment.Thank you for the comment.Nagendra Kumarhttps://www.blogger.com/profile/06536056072014454129noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-7626219670895969622021-02-09T22:03:28.042+05:302021-02-09T22:03:28.042+05:30good one. thank you for sharing :)good one. thank you for sharing :)Rupahttps://www.blogger.com/profile/08614020037253088307noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-39625445412322870572017-02-09T07:43:43.179+05:302017-02-09T07:43:43.179+05:30It seems you might have changed the IP MTU under i...It seems you might have changed the IP MTU under interface after the session is established. Make sure you have the MTU configured as 1000 on the egress interface of this BGP session and try clearing the session. It should help change the MTU.Nagendra Kumarhttps://www.blogger.com/profile/06536056072014454129noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-66768061836255685972016-12-26T13:55:53.572+05:302016-12-26T13:55:53.572+05:30I have configured IP MTU 1000 Explicitly between ...I have configured IP MTU 1000 Explicitly between R2 & R2 interface. But I am seeing the Datagram size as 1460. Should the Datagram size have been 960 ? What could be the issue?<br /><br /><br />R1#sh ip bg neighbors | i Data<br />Datagrams (max data segment is 1460 bytes):<br />!<br />R5#sh ip bg neighbors | i Data<br />Datagrams (max data segment is 1460 bytes):<br />Anonymoushttps://www.blogger.com/profile/09697326451613550693noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-41847195998135069032016-10-19T19:48:16.401+05:302016-10-19T19:48:16.401+05:30Great stuff Nagendra :)Great stuff Nagendra :)Anonymoushttps://www.blogger.com/profile/16248585908109167813noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-83092790340749515532013-12-11T00:17:14.669+05:302013-12-11T00:17:14.669+05:30Amit,
As explained in the blog, when a BGP Update...Amit,<br /><br />As explained in the blog, when a BGP Update is sent by the router, it will reset the keepalive tiemr for that neighbor and will not send any explicit keepalive for that interval. The Update itself is expected to act as a keepalive. So when a BGP Update is sent and dropped by intermittant node, the nwighbor will not reeive any update or keepalive for 180 seconds (or the holdtimer) and will reset the session.<br /><br />-NagendraNagendra Kumarhttps://www.blogger.com/profile/06536056072014454129noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-76960442720625066292013-12-02T18:13:16.166+05:302013-12-02T18:13:16.166+05:30Hi
BGP Update is of big size it is dropped by R3...Hi<br /><br /> BGP Update is of big size it is dropped by R3 , then why keepalives will not reach the R5.Keepalive message is 19 bytes so it should pass by R3.Right ??<br /><br />Thanks<br />Amit Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-1416760035298868922013-09-08T23:26:14.552+05:302013-09-08T23:26:14.552+05:30awesome explanation...awesome explanation...Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-30370405031503739682012-03-15T19:55:37.365+05:302012-03-15T19:55:37.365+05:30Hi,
If you have BGP PMTUD enabled (In certain IOS...Hi,<br /><br />If you have BGP PMTUD enabled (In certain IOS it is disabled by default), BGP packets will be sent with DF bit set.Nagendra Kumarhttps://www.blogger.com/profile/06536056072014454129noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-19410302426661380202012-01-27T18:42:02.705+05:302012-01-27T18:42:02.705+05:30Nagendra,
When I did a wireshark capture, I could...Nagendra,<br /><br />When I did a wireshark capture, I couldn't see the df-bit set on the BGP update message.<br />so do all routing protocols send their udpate pacakets with df bit set??Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-3801400300092334202011-12-04T10:02:21.154+05:302011-12-04T10:02:21.154+05:30Yes. When PMTUD is disabled, MSS will default to 5...Yes. When PMTUD is disabled, MSS will default to 536 bytes. While this works, it may result in inefficient use of the network, sending segment of size 536 bytes on link capable of handling around 9000 bytes.Nagendra Kumarhttps://www.blogger.com/profile/06536056072014454129noreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-44753894947174040512011-11-30T11:31:47.463+05:302011-11-30T11:31:47.463+05:30If ICMP is blocked between the path of 2 BGP peers...If ICMP is blocked between the path of 2 BGP peers, then PMTUD will cease to work. So if we turn off PMTUD then, it should work again (albeit, not as efficiently if fragmentation occurs), is this correct?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8872651374870949504.post-76240192412287860792010-11-08T22:49:48.718+05:302010-11-08T22:49:48.718+05:30Nice explanation. ThankxNice explanation. ThankxDMnoreply@blogger.com