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adambmedent
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BGP Route distribution

Sat Oct 08, 2022 5:02 pm

I picked up a couple CCR2116-12G-4S+ in hopes of replacing some Ubiquiti Edgerouters.

We have 3 separate ISP's and each has their own Ubiquiti Edgerouter. We do eBGP with each ISP, then iBGP between the 3 Edgerouters to share routes. This has worked great on the Ubiquiti routers.

I replaced 1 of the 3 Ubiquiti's with a CCR. I plan on replacing them all if I can get this working properly.

The eBGP to the ISP is working as expected. The CCR is receiving a full table and properly advertising our public /24 out to the ISP.

The iBGP session to the Ubiquiti routers comes up aok, but no BGP routes are sent to the Ubiquiti routers. The CCR is receiving routes from the Ubiquiti Edgerouters but its not using any of them.

If I enable Output Redistribute and select BGP, the BGP session fails to start. If I select connected or enable default originate, those routes are properly redistributed. I just can't get BGP routes to redistribute to iBGP peers

I am not sure what else is needed at this point. The documentation is lacking for v7 and 90% of the info out there is for v6 BGP.

For a router that touts BGP performance, the lacking documentation and bugs is concerning.
 
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Re: BGP Route distribution

Sat Oct 08, 2022 8:32 pm

...
I am not sure what else is needed at this point. The documentation is lacking for v7 and 90% of the info out there is for v6 BGP.

For a router that touts BGP performance, the lacking documentation and bugs is concerning.

This is not a Mikrotik issue, but the way iBGP/eBGP protocol works.

Mikrotik documentation is not there to teach you how protocols work, Mikrotik expects you to understand how protocols work, etc. Read up on split horizon / iBGP, etc to learn how this works and you will also find solution to you problem

Below might help you

https://www.youtube.com/watch?v=DmkkVNdMwhI
 
adambmedent
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Re: BGP Route distribution

Sat Oct 08, 2022 9:39 pm

I appreciate the input, but this is a Mikrotik issue. The documentation and examples are lacking. You realize I can't even run a command to see the advertised routes at this point right? This is basically a joke.

BGP is not that difficult in any other hardware I have worked with (Cisco/Adtran/Juniper/Ubiquiti). None of those vendors have given me a headache like this. In fact it was basically cake to setup. Mikrotik on the other hand in v7 seems 50% done.

I will give the video a watch, but I have a feeling there is more at play bug wise and lack of important features than my understanding of BGP.

You are correct its not mikrotik's job to ensure we know the protocols, but it is their job to provide the functionality to actually work with said protocols.
 
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Re: BGP Route distribution

Sun Oct 09, 2022 10:59 am

BGP redistributes routes received from other bgp sessions from the same instance without needing any redistribute settings enabled.
Either sessions are not from the same instance or you have set routing filters to block something.

Advertisements can be seen if you install v7.6rc and go to /routing/stats/adverts menu
 
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Re: BGP Route distribution

Sun Oct 09, 2022 3:16 pm

moderator note: do not quote preceding post, just use "Post Reply".
No route filters are set at all on the iBGP sessions. Each router has a IBGP session with one another. The 2 Ubiquiti routers are sending their routes to the CCR with no issue, but the CCR isn't doing the same.

I do have 7.6 installed and that helps slightly, but its still only half the picture. I still can't see routes advertised to the CCR, just routes its advertising.

What would be the best way to troubleshoot this?
 
jd603
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Re: BGP Route distribution

Thu Oct 13, 2022 3:27 pm

The people commenting here shouldn't be... there is an issue with iBGP routes sharing to peers by default. I had this issue when testing v7 and I rolled back to 6 until it is resolved. This is a very common configuration for an ISP or anyone who wants a good failover/performance set up and it just wasn't working on v7 for me. iBGP should share ALL routes learned from eBGP by default. I tried using some filters to allow all and some other things but nothing got me a config that works like v6 or any of the Cisco / Juniper routers. Anyone who knows what is going on here (mikrotik engineer?) please chime in, is there some kind of flag we need to add or something?
 
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Re: BGP Route distribution

Thu Oct 13, 2022 3:35 pm

ROS v7 DO share eBGP routes by default, so most likely it is a misconfiguration. For example, all BGP sessions are not part of the same instance, setting different router-ids for each session makes it run as separate instances.
 
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Re: BGP Route distribution

Sun Oct 16, 2022 5:15 pm

Well I did not see that anything was in a different instance. It did use the auto config when upgrading, maybe that broke something. I will check again when I try another deployment. There were several reasons I had to revert and that was one of them. I think the others may have been dealt with too, mostly the BGP bugs when talking to Cisco/Juniper.
 
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Re: BGP Route distribution

Fri Oct 21, 2022 11:18 pm

Hi folks, first time posing here, long time lurker.

I'm so glad I found this. I've been scraping the forums for over a week to resolve my iBGP issues.

Finally, after seeing the response above, and going back to help.mikrotik.com, I have iBGP working correctly.

I had completely overlooked in the v7 documentation, the information regarding the router-id. After carefully reading the docs I noticed the following information:
Equal router-ids are also used to group peers into one instance.
You can read more here: https://help.mikrotik.com/docs/display/ ... 0instance.

My original configuration was using different router-ids for the eBGP and iBGP sessions.

After correcting this I am able to see the routes being advertised to the iBGP peer.

Now I need to troubleshoot why a route with local preference of 80 is preferred over a route with local preference 120.

Here is the output of "routing/route/print detail where bgp dst-address=100.0.0.0/8"

The inactive BGP route (local pref 120) next hop is reachable on the loopback of the iBGP peer through OSPF.
The active BGP route (local pref 80) next is reachable on the other side of a directly connected network.
[admin@UK-IX2-SOUTH] > routing/route/print detail where bgp dst-address=100.0.0.0/8
Flags: X - disabled, F - filtered, U - unreachable, A - active;
c - connect, s - static, r - rip, b - bgp, o - ospf, d - dhcp, v - vpn, m - modem, a - ldp-address, l - ldp-mapping, y - copy;
H - hw-offloaded; + - ecmp, B - blackhole
  b   afi=ip4 contribution=best-candidate dst-address=100.0.0.0/8 routing-table=main gateway=10.255.255.1
       immediate-gw=10.0.0.1%ether3 distance=200 scope=40 target-scope=30 belongs-to="bgp-IP-10.255.255.1"
       bgp.peer-cache-id=*B000003 .as-path="1264" .communities=1111:120 .local-pref=120 .atomic-aggregate=yes .origin=igp
       debug.fwp-ptr=0x20342360

 Ab   afi=ip4 contribution=active dst-address=100.0.0.0/8 routing-table=main gateway=100.0.2.1
       immediate-gw=100.0.2.1%ether1 distance=20 scope=40 target-scope=10 belongs-to="bgp-IP-100.0.2.1"
       bgp.peer-cache-id=*B000001 .as-path="1264" .communities=1111:80 .local-pref=80 .atomic-aggregate=no .origin=igp
       debug.fwp-ptr=0x203422A0
[admin@UK-IX2-SOUTH] >

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