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millenium7
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MPLS/VPLS will not form between iBGP neighbors

Tue Jun 19, 2018 4:47 pm

I'm not sure if this is a BGP issue or whatnot, but we have a section of our network that joins 2 area 0 OSPF networks together via iBGP route redistribution on both sides (they are physically connected over a wireless ptp link)
I have MPLS and VPLS running in many areas of our network without an issue. However in this case they simply will not connect to each other

- I have set the transport address to the loopback IP's (same as everywhere else in the network)
- I have triple checked that MTU is fine along the path (capable of 9600 between them)
- Both routers can see each others loopbacks in their routing tables
- Both routers can ping each others loopbacks, 1 total hop
- The MPLS LDP neighbor state goes to DOT
- The loopback addresses or any other remote addresses do not appear in the MPLS forwarding table
- I cannot establish a VPLS tunnel between these 2 routers (there are no other routers between them)
- Both routers have no firewall rules at all

If I change the LSR transport address to the interface IP instead of the loopback IP on both sides, and also change the remote IP of the VPLS tunnel to the other sides interface IP it works. But this is not a solution. I don't need VPLS between these 2 routers, I actually need VPLS between 2 much further away routers, but this link is the problem that I need to solve first
Is iBGP the problem here or something else?
 
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Anumrak
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Re: MPLS/VPLS will not form between iBGP neighbors

Tue Jun 19, 2018 4:57 pm

BGP is not involved in VPLS. For VPLS you using LDP signaling in martini draft. So just create ospf routing, ldp neighbors and run vpls. If you can't establish vpls tunnel between loopbacks, then you might have a problem in ldp connectivity.
 
millenium7
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Re: MPLS/VPLS will not form between iBGP neighbors

Wed Jun 20, 2018 6:34 am

I can't use OSPF because this segment is bridging 2 separate OSPF area 0 networks together. I don't want each side involved and I don't want to convert a side to another area. It's easy just to use BGP to redistribute routes. Plus there are 2 paths and OSPF convergence time is too slow because it doesn't keep the backup route in the table, BGP does

MPLS doesn't seem to form correctly either when using loopback addresses, no routes show up.in the MPLS table. Is BGP causing an issue here or is it going to be something else? Maybe I need to configure something extra in BGP?
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 10:25 am

I can't use OSPF because this segment is bridging 2 separate OSPF area 0 networks together. I don't want each side involved and I don't want to convert a side to another area. It's easy just to use BGP to redistribute routes. Plus there are 2 paths and OSPF convergence time is too slow because it doesn't keep the backup route in the table, BGP does

MPLS doesn't seem to form correctly either when using loopback addresses, no routes show up.in the MPLS table. Is BGP causing an issue here or is it going to be something else? Maybe I need to configure something extra in BGP?
Why you think that OSPF can't keep different reserve routes? It can just like EIGRP, maybe with a little slower convergence, but it can. If you need to know link info on routers, then you should use OSPF, if you need to just signal routes use BGP. MPLS need only for seemless BGP connectivity between their neighbors. With MPLS there is no need to BGP full mesh topology. And of course you can advertise different routing tables between BGP neighbors over MPLS, that is called MP-BGP. BGP can filter l3 VPN routes and IPv4/v6 routes more efficiently than OSPF.

If your BGP neighbors can't establish connectivity because of absent loopback IP in LDB table of MPLS, then you should troubleshoot this spot.
 
millenium7
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:08 am

This is definitely a BGP issue
I've setup a lab to replicate the topology. If I use OSPF it works fine, if I use static routes it works fine, if I use BGP it doesn't
Loopback addresses do not appear in the MPLS bindings and hence VPLS will not form
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:13 am

This is definitely a BGP issue
I've setup a lab to replicate the topology. If I use OSPF it works fine, if I use static routes it works fine, if I use BGP it doesn't
Loopback addresses do not appear in the MPLS bindings and hence VPLS will not form
Did you make BGP full mesh? Each neighbor with each other. Like 1-2-3-4, or just 1-4?
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:15 am


Why you think that OSPF can't keep different reserve routes? It can just like EIGRP, maybe with a little slower convergence, but it can. If you need to know link info on routers, then you should use OSPF, if you need to just signal routes use BGP. MPLS need only for seemless BGP connectivity between their neighbors. With MPLS there is no need to BGP full mesh topology. And of course you can advertise different routing tables between BGP neighbors over MPLS, that is called MP-BGP. BGP can filter l3 VPN routes and IPv4/v6 routes more efficiently than OSPF.

If your BGP neighbors can't establish connectivity because of absent loopback IP in LDB table of MPLS, then you should troubleshoot this spot.
OSPF doesn't keep reserve routes. It detects a change, waits for everyone to agree on the new topology and then calculates a new route. This is not at all like EIGRP (I really wish MikroTik would implement EIGRP as it has many benefits in a lot of instances)
The 2 routers in question are joining 2 separate OSPF area 0 networks together. I do not want to join them all into 1 much larger one - reconvergence will become MUCH slower - and I also want the ability to summarize. I can't summarize anywhere except ABR/ASBR in OSPF (again, EIGRP would have been great). I'm using BGP for convergence time and summarization at this point in the network. If I create a separate area i.e. area1 it will cause issues due to having 2 separate area 0
Did you make BGP full mesh? Each neighbor with each other. Like 1-2-3-4, or just 1-4?
There are only these 2 routers doing BGP at this point, so yes its technically a full mesh since there's only 2 routers participating in that AS
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:20 am

Did you redistribute connected network?
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:23 am

Yes, have also tried manually adding networks, doesn't seem to matter. Still does not work
As soon as I add a static route (which overrides the BGP route) - with exactly the same gateway - it works. Disable the static route, stops working
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:25 am

I reditributed loopbacks in OSPF. Client networks I redistrubute in BGP. Strange. WIll try redist loopback in BGP at home.
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 11:39 am

Try to advertise loopback with routing filter. Like: /routing bgp peer set out-filter=ISP1-out. In filter sign 1.1.1.1/32 for example. Something like that.
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 12:15 pm

Nope. The route it is in the routing table with BGP just fine, just that MPLS doesn't seem to care
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 12:16 pm

LDP will not assign labels to BGP routes
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 12:29 pm

LDP will not assign labels to BGP routes
Why? It does, when BGP configured as nexthop­choice=force­self with address known from OSPF. Correct me with expand answer if I wrong.

Like this:
Image
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 1:40 pm

LDP will not assign labels to BGP routes
Is there any way around this?
I could set a static IP for the next router i.e.
A-B
And then it works I can get a VPLS tunnel between those 2 routers
But VPLS doesn't work for routers that are further along i..e
A-B-C (between A and C)

I even tried setting a static route to C on A (with recursive lookup) it doesn't work. Even if it did this is not a solution because its not scalable setting up static routes for every VPLS connection
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 1:57 pm

LDP will not assign labels to BGP routes
Is there any way around this?
I could set a static IP for the next router i.e.
A-B
And then it works I can get a VPLS tunnel between those 2 routers
But VPLS doesn't work for routers that are further along i..e
A-B-C (between A and C)

I even tried setting a static route to C on A (with recursive lookup) it doesn't work. Even if it did this is not a solution because its not scalable setting up static routes for every VPLS connection
mrz meant that ldp creates labels only for OSPF network as for link state protocol, also LDP creates labels for OSPF loopback addresses. But if you configure BGP peers with option nexthop self force with BGP update source - loopback interface, BGP peer will advertise route which will be reachable via OSPF loopback = mean LDP = mean label creation. Maybe you didn't set nexthop self force to BGP peer?

Also this option is very nice to set on all LDP routers: propagate-ttl=no, in order to see whole MPLS cloud as one IP hop.
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 2:25 pm

Yes I have tried that but I am not running OSPF between these 2 routers. Let me draw a basic diagram that will make more sense

Image

I don't want to join the OSPF area's because then a change on router F will mean routers A/B/C/D hear about it
1) Slower convergence
2) No ability to summarize
3) Larger routing tables
4) Problem with fragmented area 0 if D-E link goes down

I don't want to convert an entire area to i.e. Area5 because it's a lot of work and provides no benefit to us
(EIGRP would be perfect for us, pretty please MikroTik)
The reason i'm using BGP is for summarization, smaller routing tables on all routers except D and E, and fast failover (there are actually 2 links between D and E but for simplicity lets just pretend there is only 1)

So the question is whats the best method here for scalability? We need the ability to establish VPLS tunnels between sites on each side. I obviously can't use something that requires setup on every single router every time we add a VPLS tunnel
Will BGP signalled VPLS work if I implement it only on D and E? Or would I need to run it on A & I (which then over time would mean A & E/F/G/H/I as well as G & A/B/C/D due to further growth and need to transport more VPLS across D-E)
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 2:36 pm

What I have done before is run 2 OSPF instances on D & E, then I redistribute between both instances. But I have had some routing issues where traffic went across D-E when it didn't have to. And I don't have as much flexibility. It generally just seems quite messy
Moving to BGP I have not had issues, except VPLS........
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Thu Jun 21, 2018 3:59 pm

All I can see is you wanna do a trick in OSPF that will allow you run MPLS through OSPF without OSPF on E & D :) And you wanna run BGP that will segment 2 simmilar OSPF domains which had to be in different areas.

If you don't want to show some routes to routers A,B,C,D, then use routing filters for OSPF process. If you want faster convergence, use BFD between spots you wan fast conv.

In order to run MPLS/VPLS you have to make smooth OSPF domain without BGP between. Don't do worst design with things that have to run another way.
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Fri Jun 22, 2018 4:08 am

Don't do worst design with things that have to run another way.
You mean like using OSPF instead of EIGRP? :)

It would be PERFECT for our network, and quite honestly I imagine it would also be perfect for the vast majority of WISPs. I'm surprised MikroTik hasn't implemented it (it is not Cisco proprietary anymore) because while OSPF works very well when planned from the start with a large topology, all hardwired links and segmented growth. It does not fit so well with many with growing WISPs that go from a single link to large scale - often buying other businesses along the work and incorporating their networks, with lots of spokes and chained links. Merging multiple area 0's is not fun, and often not easy to do 'properly'

I'm going to investigate if BGP signalled VPLS will work. I may have to go back to using 2 OSPF processes and redistribution but i'd rather avoid it if I can, if anyone has other idea's please let me know
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Fri Jun 22, 2018 7:16 am

I think BGP signalled VPLS might work but i'm having reliability issues. I've never configured this before so maybe i'm doing something wrong, I did follow the wiki but.... well the first problem is MPLS does not form without LDP, so even though BGP is working, i'm using L2VPN functionality and both routers create a dynamic VPLS interface, it does not enter the running state. I have to enable LDP in order to get the labels in MPLS. Huh???? I thought the whole point of BGP in this instance is you can completely disable LDP as it does the signalling

Ok so I enable LDP and it works.... sometimes..... I find I have to toggle VPLS BGP on and off a few times to get actual packet flow. I mean sure the tunnel says its running, and the neighbor shows up under IP->Neighbors, but I can't mac ping or normal ping. So I toggle it off and back on a few times and it starts working again. This problem gets much worse once I start adding in other nodes. I tried adding another router into the BGP process and I have the same problem, sometimes it works, but I have to toggle things on and off and with 3 routers participating I sometimes have to toggle things on and off a dozen times. With 4 routers I managed to get it to work once or twice and thats it. This is incredibly unreliable, maybe LDP is the issue but as above i'm not able to get MPLS to get any labels using just MP-BGP
 
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Re: MPLS/VPLS will not form between iBGP neighbors

Fri Jun 22, 2018 8:44 am

Can you post the routing table from each side of the VPLS in question along with the configuration? Obfuscate the passwords and public (if any) IPs
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Re: MPLS/VPLS will not form between iBGP neighbors

Fri Jun 22, 2018 10:02 am

I think BGP signalled VPLS might work but i'm having reliability issues. I've never configured this before so maybe i'm doing something wrong, I did follow the wiki but.... well the first problem is MPLS does not form without LDP, so even though BGP is working, i'm using L2VPN functionality and both routers create a dynamic VPLS interface, it does not enter the running state. I have to enable LDP in order to get the labels in MPLS. Huh???? I thought the whole point of BGP in this instance is you can completely disable LDP as it does the signalling

Ok so I enable LDP and it works.... sometimes..... I find I have to toggle VPLS BGP on and off a few times to get actual packet flow. I mean sure the tunnel says its running, and the neighbor shows up under IP->Neighbors, but I can't mac ping or normal ping. So I toggle it off and back on a few times and it starts working again. This problem gets much worse once I start adding in other nodes. I tried adding another router into the BGP process and I have the same problem, sometimes it works, but I have to toggle things on and off and with 3 routers participating I sometimes have to toggle things on and off a dozen times. With 4 routers I managed to get it to work once or twice and thats it. This is incredibly unreliable, maybe LDP is the issue but as above i'm not able to get MPLS to get any labels using just MP-BGP
The simpler the topology, the better for the network and better for its support.

If I was you, I'd choose one OSPF area for all routers and VPLS with LDP signaling.
 
millenium7
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Re: MPLS/VPLS will not form between iBGP neighbors

Fri Jun 22, 2018 11:11 am

The simpler the topology, the better for the network and better for its support.

If I was you, I'd choose one OSPF area for all routers and VPLS with LDP signaling.
RIP is simple, but we don't use RIP because it's slow and inefficient. Same with a very large area0 topology across many wireless links. I've seen OSPF reconvergence times in the minutes when it gets too large
It's a link state protocol, every router must agree on the entire topology in the same area 'before' link calculations are done and routes are put into the routing table. This is really bad if there's i.e. a flapping link. And a split area 0 topology is really bad.
So while having the whole network as just 1 flat area is 'simple' it's far from a good design

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