BGP ECMP (multipathing)

RouterOS Forwarding Protocols
1

Hi There

I have setup where the Customer router (Router Boards) is connected to a MPLS ELAN (VPLS) cloud provided by a third party. We, the ISP are connected redundantly to that cloud with two Cisco Routers. I now set up two BGP
sessions from the Customer Routers to the ISP Routers for redundancy and announce the Prefix the Customer gets assigned and send a default route to them from the Cisco routers.

I now like to do load balancing over these two default gateways. I know that MikroTik has the standpoint that BGP can not do ECMP by design, but all other vendors I know can do it (Cisco, Juniper, Brocade, Fortinet etc.)

As the two BGP sessions do not end on the same router I can not use the loopback method mentioned in the BGP ECMP manual here: http://wiki.mikrotik.com/wiki/Manual:BGP_Load_Balancing_with_two_interfaces
But they reference a Cisco page to explain that other vendors do it the same way and that this is only the right way… fortunately on this same page Cisco explains how BGP multipath works! http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml (Load Sharing When Dual-Homed to One Internet Service Provider (ISP) Through a Single Local Router)

Will MikroTik reconsider their standpoint about multipath BGP or do I have to switch back to Cisco for the customer routers?

Regards

Matthias

2

It is a hack and we also can do it.
http://wiki.mikrotik.com/wiki/Manual:BGP_Load_Balancing_with_two_interfaces

3

Please explain how this is different to what I already wrote. Loopbacks are not possible. There are two (2) BGP sessions to two (2) different routers. So the destination can not be the same.

Or am I wrong ?

Regards

Matthias

4

Read that cisco article and mikrotik article, they both uses the same principle and loopback address.

5

Have you red the section: Load Sharing When Dual-Homed to One Internet Service Provider (ISP) Through a Single Local Router


This is what I like to accomplish. The other examples are clear and is common practice, I agree…

6

This is exactly the same setup as Load Sharing with the Loopback Address as a BGP Neighbor except that remote end has two routers.
Setup on mikrotik router would be the same, both remote peers establishes BGP session to loopback address.

7

Remote peers are not the problem. I want two default routes on the Mikrotik to the remote peers. That does not change anything if I make a session to remote peer loopbacks.

8

So to make it clear you have two BGP R1 and R2 running iBGP between then. They bothhave peering to ISPs router (R3).
And you want to have ECMP routes on R1 and R2?
R1------------
|
ibgp ISP R3
| /
R2------------/

9

No, the other way around:

    +-------------- ISP_R1 -+
    |   EBGP                |
 R1-+                       | IBGP
    |   EBGP                |
    +-------------- ISP_R2 -+

R1 is Mikrotik
ISP_R1 and R2 are Cisco

10

Then the same setup as described in the manual
R1 has loopback address and both ISP routers should establish connection to loopback. Exact same config is also in cisco article.

11

Yes, exactly … But with the little command “maximum-paths 2” in the bgp config!

12

It just limits ecmp gateways to two. Mikrotik does not limit amount of gateways.

13

So then the missing A on route 1 does not mean anything ?

> /ip route print
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme, B - blackhole, U - unreachable, P - prohibit 
 #      DST-ADDRESS        PREF-SRC        GATEWAY            DISTANCE
 0 ADb  0.0.0.0/0                          212.25.9.1               20
 1  Db  0.0.0.0/0                          212.25.9.2               20

If I make traceroutes from a public ip behind the mikrotik (no nat) to several locations, it always takes the path over route 0.

14

And now there is silence …
Are you now convinced that there should be a “maximum-path” feature like in cisco ios to accomplish this? Or am I just to boring to be eligible for a rely.

15

maybe, post at least your BGP config first?..

16

Shure, here ist the relevan config of the mikrotik router.

# feb/02/1970 15:21:57 by RouterOS 6.7
# software id = XHEM-GX3Y
#
/interface vlan
add comment="CES" interface=sfp1 l2mtu=4070 mtu=4000 name=sfp1-ces vlan-id=3214
/ip neighbor discovery
set sfp1-ces comment="CES"
/interface wireless security-profiles
/routing bgp instance
set default as=64512 router-id=z.y.x.w
add address=z.y.x.w/26 interface=sfp1-ces network=z.y.x.0
/routing bgp network
add network=a.b.c.d/27 synchronize=no
/routing bgp peer
add name=peerA remote-address=z.y.x.1 remote-as=8758 ttl=default update-source=sfp1-ces
add name=peerB remote-address=z.y.x.2 remote-as=8758 ttl=default update-source=sfp1-ces

peerA and peerB are Cisco Routers, which only announce a default route.
I’m happy for any inputs

17

Ok, sorry for that. Yes you are right your intended setup is currently not possible on MikroTik routers. BGP will install only one gateway.

18

Thanks for your confirmation. At least I know now that I’m not doing something wrong. Are there plans to support this? Would be a very nice and appreciated feature.

19

I am really disappointed to see that this is not supported. We have 4 CCR1036-8G-2S+EMs in production that I need to do this to coming up.

What can we do to get this feature implemented? We have been migrating away from Cisco to Mikrotik, but missing features like this are really hurting us.

20

Please add suport for many (2-3) ways for gateway for BGP