Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

MTU PMTUD

Posted on 2014-11-23
1
Medium Priority
?
197 Views
Last Modified: 2014-11-24
I know how Routers handle MTU restriction issues using ICMP return messaged to inform the originating host of the packet size issue and for the host to reduce its payload.

Just curious how this is dealt with in the Data Center where the fabric is layer 2 for the most part?
0
Comment
Question by:sectel
1 Comment
 
LVL 18

Accepted Solution

by:
Garry Glendown earned 2000 total points
ID: 40461517
On a pure L2 connection, incoming frames larger than the configured MTU will be dropped. You may get error messages on the device, though that depends on the vendor and configuration.
For incoming frames that are still OK for that port, but too large for the outgoing port (not sure if that can happen on a switch, though - normally the MTU/Jumbo MTU is configured system-wide, not per port, and then left to Layer 3 to complain about), a signal might be sent to L3+ to notify the sending station, though I haven't seen such an option on any device I've come across.
In short - make sure all your switches are configured for large enough frames to allow for any current and future use case (we typically configure 1600 MTU and maximum allowed MTU, which is 9198 on Cisco switches IIRC, for Jumbo MTU ... the first will comfortably take care of any L2 switching and VLAN options like 1Q, as well as MPLS label stacks, the latter for high speed links with server interconnects etc.). This is especially important as some devices may require a reboot to change system-wide MTUs
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

How to set-up an On Demand, IPSec, Site to SIte, VPN from a Draytek Vigor Router to a Cyberoam UTM Appliance. A concise guide to the settings required on both devices
This article will show how Aten was able to supply easy management and control for Artear's video walls and wide range display configurations of their newsroom.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

581 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question