[j-nsp] Juniper MX240 to Alcatel SAS-M epipe

Tomasz Mikołajek tmikolajek at gmail.com
Thu Aug 8 17:07:54 EDT 2013

OK, I ping OLT from MX like you Saku wrote and i get information:

With JunOS, the size you specify on the ping command is actually the size
of the ICMP payload.  1472 of payload + 8 bytes of ICMP header + 20 bytes
of IP header results in a 1500 bytes IP packet, which is the largest packet
you can send without fragmentation.

When i ping OLT with 1500 I don't get respons. L2circuit/epipe is up, isis
adj is up. No every website work eg. ripe.net Where is the problem?

2013/8/7 Saku Ytti <saku at ytti.fi>

> On (2013-08-07 17:43 +0200), Mark Tinka wrote:
> > True, but the OP suggested that some of the web sites he's
> > browsing don't load correctly, which could allude to an MTU
> > issue in the data plane.
> Mea culpa, luckily point remains it does not matter what the eline MTU is.
> Fully agreed on your suggestion that just guarantee core is large enough,
> no point doing 'exactly the right size' but large enough.
> For sake of argument 'exactly the right size' in untagged ethernet core
> 6B DMAC (not calculated by IOS)
> 6B SMAC (not calculated by IOS)
> 2B type (not calculated by IOS)
> 4B IGP label
> 4B VPN label
> 4B control word (maybe, maybe not)
> 6B inner DMAC
> 6B inner SMAC
> 2B inner type
> xB payload
> 4B FCS (not calculated by IOS or JunOS)
> It might be prudent to figure out customer experienced MTU by doing over
> the l2circuit:
> a) ping with 1500B DF set
> b) ping with 1501B DF not set
> --
>   ++ytti
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