04-18-2007 12:14 AM
Hello, after reading previous post about NAT, i don't have very clear how to resolve my problem.
I'm using a MPLS-VPN to connect different sites to a central site providing internet access with a PIX (old device, PIX 520 6.1), anf i've found those known problems when using PAT (users not nagating in www.hotmail.com and more)
USER - CE - PE - MPLS - PE - PIX - INET
i have configured every link in the MPLS path with MTU 1516 and tag-switching mtu 1512. And links over pure IP with MTU 1500
04-24-2007 08:17 AM
Perform this task to set the MTU on the local hosts. Network Address Translation (NAT) does not have to be configured to specify the MTU. Refer URL
05-02-2007 12:20 AM
Hi,
Another aproach is to enable the core routers to accommodate all packets.
The MTU should be greater than or equal to the total bytes of the items in the following equation:
Core MTU >= (Edge MTU + Transport header + AToM header + (MPLS label stack * MPLS label
size))
Edge MTU + Transport header + AToM header + (MPLS label stack * MPLS Label) = Core MTU
1500 + 18 + 0 + (2 * 4 ) = 1526
You must configure the P and PE routers in the core to accept packets of 1526 bytes. See the following section for setting the MTU size on the P and PE routers.
As you have indicated some interfaces (such as FastEthernet interfaces) require the mpls mtu command to change the MTU size.
Hope this helps.
Regards Bjornarsb
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