[nsp] increased Ethernet MTU on 7200

[Iwan Thomas]

I have a long-standing TAC case open for this. It seems likely that the 7200
and 7500 FE PA hardware cannot deal with the following on the uplink from
the PE:

1500	customer payload inc IP header
18 	customer ethernet header with 802.1q
4	AtoM control header
4	MPLS vc label
4 	MPLS LDP label
18 	provider ethernet header
----
1548

the largest packet the customer can send is 1498. 

Anyone else observed this? The 'show controller' command doesn't work on my
7505 running 12.0(23)S

> -----Original Message-----
> From: Stefan Stefanov [mailto:sstefanov at orbitel.bg]
> Sent: 27 May 2003 09:55
> To: Rainer
> Cc: Discussion for Network Service Provider
> Subject: Re: [nsp] increased Ethernet MTU on 7200
> 
> 
> Been through this pain some time ago....
> 
> On IO-2FE you can have 1528 bytes of max MTU. To achieve this you have
> to create a 802.1q vlan sub-interface. Without this you are bound to
> 1524 bytes.
> 
> This should be sufficient for MPLS + ATOM over FastEthernet in most
> cases (1500 bytes customer MTU with Frame Relay, HDLC and 802.1q
> encapsulations).
> 
> On this controller you can see the maximum MTU with the show 
> contr fa0/0
> and search for max_mtu:
> 
> rtr>sh controllers fa0/1 | inc max_mtu
>   max_mtu=1528
> 
> Hope this helps.
> 
> Stefan
> 
> On вт, 2003-05-27 at 11:37, Rainer wrote:
> > Hello,
> > 
> > is it possible to increase the MTU on any Ethernet 
> interface available
> > for 7200 routers? Searching cisco.com or googling around 
> didn't turn up
> > anything helpful.
> > 
> > So far I had no luck with io-2fe, io-1fe-tx-isl and pa-1fa-tx-isl.
> > 
> > 
> > Rainer
> > 
> > -- 
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> 0556 E25A 7599 75BD
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> -- 
> Best Regards,
> 
> Stefan Stefanov
> CTO
> Orbitel, Inc.
> tel.: +359 2 937 07 20 fax: +359 2 980 42 58
> 
> 
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