| Working with EoMPLS Part 2 |
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In that blog, we discovered that setting up port-based EoMPLS is darn easy. So easy that the danger is creating mounds of L2 spaghetti on top of your robust L3 routed network. (Yes I've had dinner, there's no food craving at work here!) This blog is a quick follow-up to that blog. It posts tested configlets for VLAN-based EoMPLS. I recently did some VLAN-based EoMPLS in the lab using dot1q subinterfaces on a 7200 router using GNS3 / Dynamips. The configuration is nearly identical.
VLAN-Based EoMPLS on a 6500Update, 1/5/2010: It's been suggested that I provide a picture. Indeed, I'd have liked to, but time has been a bit tight. The picture is darn simple: swA, links/cloud, swC. I've also been asked for the configs for what's in between. However, that would just obscure the simplicity -- the links in between need IP routing and "mpls ip" enabled on them (and preferably on alternate paths as well). And the interface MTU cranked up / jumbos, I've been using the biggest number allowed. Here are representative configurations for two 6500's running EoMPLS using OSPF routing and LDP on the paths between the endpoint switches. Really, only routes between the loopback addresses (1.1.1.1 and 2.2.2.2 below) are needed.
Once the overall port MTU was correct, the VLAN-based xconnect came up. (That's why I show it in the above configlets.) Note that this does NOT locally switch VLAN 200 into the xconnect when configured on a switch. It takes incoming frames tagged with VLAN 200 dot1q tagging and forwards them to the port at the other end, with relevant VLAN tagging. Connecting the physical port back to the switch, with trunking and appropriate VLAN tagging, is required to obtain local switching. This is similar to what was observed for port-based xconnect, but requires more configuration. Not triedI haven't tried port-based EoMPLS on a 7200 router. Or rather, I tried hastily in GNS3, didn't see the command options I expected, and shifted to VLAN-based since that worked for what I needed to do. I did a quick Google search for configuration for port-based EoMPLS in router IOS, and I'm not seeing anything obvious as an example, so I'm kind of curious to see if it can be done. Of course, one can use QinQ on a switch to feed tagged frames into a VLAN-based EoMPLS pseudo-wire, but that's not a very direct way to get the job done. Update, 1/5/2010: Per CNC's Luan Nguyen (and his CCIE SP prep), port-based EoMPLS on 7200 is easy: just put the xconnect on the main interface. I had tried that, but it was apparently not supported in the images I tried. ("xconnect ... encaps mpls" was not an option). I tried again with a 15.0 image for the 7200 and it worked. I still claim that this is not documented, or at least I sure didn't find it explicitly shown in the IOS docs, nor in the examples Google found for me. (Or I was having prolonged blindness to what was in front of me?) So that's darn easy, and thanks to Luan. I also haven't lab-tested doing port-based EoMPLS with different VLAN-based pseudo-wires going to different destinations. On the other hand, it's clear how to configure that, and I have no reason to expect it to not work. RecommendationsWhen in doubt, consider using port-based xconnect, it requires less configuration on the endpoints. Use VLAN-based EoMPLS if you want the VLANs to act sort of like Frame Relay DLCI's, with different VLANs going to different other endpoints. |
A previous article took a look at Port-Based EoMPLS on a 6500. See 