A large network that is running VPLS has been working quite well. We currently are not worried about packet fragmentation, however, we can not push the 1500 byte MTU packets though the VPLS in some instances.
VPLS circuits are set to 1508 in MTU in case of VLAN information, the VPLS tunnels do come up. In most cases, we have had the VPLS tunnels up for several weeks or longer, then in the morning, we come in and have calls about customer issues. We check, the VPLS circuit is up, but the largest ping we can get though is 1442. In many cases we can simply remove the MPLS interfaces, and readd them, upon readding the VPLS comes back up and we can ping 1500 byte packets across the link.
The question is WHY does this stop working? We have tried BGP VPLS as well, but still 1442 pings only. Whats even more confusing, is we have another VPLS tunnel that goes THOUGH the affected site, and it does not have the MTU issue!
Sorry for not being of much help here, but I thought at least I should tell you that I see the same behavior for quite some time now.
On the one affected tower I even replaced the RB450G with an RB1100, and the problem was gone for months.
Thought I had it tackled. But now it is back. No changes have been made recently.
As you stated, tunnels to other sites, going through this one, are NOT affected.
Really strange.
I have this problem too but only so far with 5.12 and 5.13
5.7 or earlier I never saw this. Had to downgrade.
A while can go by and everything is OK, but then suddenly the packets size that fits is suddenly smaller.
I couldn’t ever find a way to hot fix it like you did.
Yes! I even have the same issue, packets will go THRU the router to one farther up and it works!
Still the same here.
The one affected RB1100 is on 4.17 right now, and the problem persists, but only on ether6.
Re-routing (OSPF) over to ether1 and problem is gone.
make sure you have added all interfaces used by label switching in “/mpls interface” menu, for some customers thatwas the problem, they for got to add one interface in one router in MPLS cloud.
Suddenly the VPLS-Interface stops working with 1500 Bytes. Checked it with a Customer. The Maximum was 1442 Bytes (+ PPPoE-Overhead) which goes through the tunnel.
Hardware between Customer and Core: 3xRouterboard 1100AHx2 and 1xRouterboard 1100AH (all with Version 5.14)
Double checked everything (all used Interfaces included in MPLS-Interface with MTU 1530).
Nothing has changed from our side. Only our carrier switched our leased line on another fibre-pair in the night before, so that the line was offline for about 3 hours and then the ospf-routing and mpls/vpls comes up again but with a smaller MTU within the VPLS.
We just started to implement a pure MTIK MPLS environement in our core network so please Mikrotik give us a hint how to solve this.
There are several leased lines from data center to locations over the carrier ethernet. It´s SDH and they say they give us a MTU-Size of 9600.
On friday as we noticed it, we made a ticket and they measured the line with no success.
All of our other leased lines work with VPLS 1500.
after the affected leased line is one mpls-router (with vpls-termination). this one works with 1500 bytes. After that there is a licensed radio to the affected routerboard which dont get the 1500 bytes.
There are three vpls-tunnels. I checked the mtu on all tunnels. one can handle 1446 bytes (including icmp-header), one with 1478 and one 1470. that´s really strange.
In the core there is vpls-terminator and from there are several vpls tunnels to the locations.
I readded the mpls interfaces, rebooted all routers to the customers and recreated the vpls tunnels.
i know it´s hard to give some advice for this, but everything worked like a charm before and the other users in the forum noticed this strange behavior before.
changed Routerboard at customer-site ->nothing changed
changed the middle Routerboard → nothing changed
tested the MTU-Size more accurate:
1478 Bytes is what i get on all vpls-tunnels at the customer-site. In the middle between data center and customer-site i get 1500 Bytes on all vpls-tunnels, so the leased line is definitly ok.
Between the customer-site and the middle Routerboard is a licensed radio which is capable of jumbo frames so i think thats not the problem.
Now, where are my 22 Bytes
This is getting me crazy, because it worked before without any problems and suddenly it stops.
The other vpls-tunnels on the other sites work like a charm so i dont think the routerboard within the data center is the problem.
Replaced all Routers on this line to the customers including the one in the data center. (now 3x RB1100AHx2 with RouterOS 5.19)
All routers are configured manually from the scratch.
Same problem. The VPLS-Tunnel to place 1 works with 1500 Bytes and the VPLS-Tunnel to place 2 only with 1478 Bytes.
This is not working:
Now I changed the config in this way that I create a new VPLS-Tunnel between place 1 and place 2 and attach both tunnels to a new bridge.
The OSPF interface mode are set to PTMP on the used interfaces.
This is working:
So where is my mistake? Why is it working with two tunnels and a bridge between and not with one tunnel directly from the data center?
So the licensed radio doesn´t cause the problem. I checked it with the support of our dealer, it´s capable of jumbo frames.
In another part of the network a have the same constellation (3x RB 1100AHx2 with version 5.14 and 5.19 in a row). The only thing which is different is instead of a licensed radio there is a 5GHz Ubiquiti Link (with the new mac address allowing frames bigger than 1518 Bytes for MPLS). And there is no problem. Same config except the routing part. Between data center and place 1 there is ospf network mode ptmp and between place 1 and 2 there is nbma.
Thank you for some hints. This problems causes a lot of headaches
saw this post and thought I would throw my two pesos in as I do a lot of MPLS work in Cisco and Mikrotik.
Not sure if any of you guys have tried this, but if you want to do EoMPLS/VPLS and pass a 1500 byte IP packet between the two connected hosts on the CE routers, then the MPLS MTU (and hence the max L2MTU) has to be at least 1526 for untagged frames and 1530 for tagged frames. You should be able to ping with the fragment bit set at 1472 bytes to test passing a full 1500 byte packet (you lose 20 bytes for the IP header and 8 bytes for ICMP hence 1472)
Basically with VPLS you have to have additional mtu overhead because you are encapsulating a Layer 2 frame inside of an MPLS packet and it has to have an ethernet header to deliver once it gets there so there’s 14 bytes plus a 4 byte VPLS header and the standard 8 bytes for MPLS…which gets you to 1526. So whatever the max L2 MTU is on your interface is, subtract 26 bytes and you will get the VPLS payload
Also, if you’re setting different MPLS mtus on each router, then you can potentially run into issues. it’s better to set them all to the lowest common denominator in the path.
