[c-nsp] L2TP LAC and MPLS on the same box?

Ross Halliday ross.halliday at wtccommunications.ca
Thu Oct 24 14:50:46 EDT 2013

> > Using Cisco 7301s with 15.2(4)S2, features I need are the usual unicast
> > MPLS L3VPN stuff with an IS-IS core and BGP, L2TP LAC, some BFD would be
> > nice, and IRB to bridge a single VLAN (long story of legacy
> infrastructure
> > and 6500 limitations). The 7301s run 1 GB RAM. I'm expecting up to 600
> > subs and 200 Mbps of PPPoE coming into each box.
> >
> Never mind - just found out that MPLS not compatible with IRB on these
> boxen

Well list, for anybody who may search this in the future, I found a way around using IRB (I totally forgot I had a pile of PA-2FE-TX in the back... cool!) and I've tested this.

For a 7301 as an L2TP LAC, a single user running ~50Mbps speed tests through our Ericsson SE-600 to the Ookla widget put the CPU to about 15-17%. I have not observed a difference in system performance between a traditional design with IP routing and a bunch of VLANs everywhere and running everything into MPLS. What I have noticed is that a 7301 upstream unsurprisingly has lower CPU load when it functions as an LSR. 5-7% observed with full IP routing, 3-5% under MPLS. The legacy VLAN I'm transporting is just used for management so I am not concerned about the performance impact the EoMPLS VC may have on the L2TP side of things.

All of my other features function as expected. Base load includes ~70 ISIS routes, ~4400 BGP VPNv4 prefixes, and a handful of sub-second BFD and HSRP sessions.

Field testing will show how reliable and scalable it is. It certainly appears that the duo of them should handle 500 Mbps without hassle.

Thanks to the few who replied off-list earlier.


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