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RIP route consolidation

Posted: Fri Oct 09, 2015 11:03 am
by tonny
Hi,

We've created a network of 50 (and growing) Mikrotik routers. Each router has 3 local networks with subnets
10.x.10.y /24
10.x.60.y /24
10.x.80.y /24
where x represents the location number and y is assigned by dhcp in the mikrotik. All mikrotik's can see each other via the wan interface using 172.16.1.x / 24 where x is again the location number. On that 172.16.1.x network we use RIP2.
RIP2 has been selected for we have a PBX there that can either use static routing or listen to RIP2. However I've just found out the routing table in the PBX is limited.

Is there a way to force the mikrotik's to announce a consolidated route? so instead of announcing the three connected routes individually, i want them to announce 10.x.0.0/16


Kind regards
Tonny

Posted: Sun Oct 11, 2015 4:06 pm
by shaoranrch
I think you can achieve this using prefix lists and placing said lists on the interface facing the WAN of each router. I haven't tried this but I would try the following:

Router 1
Routes
10.1.1.0/24
10.1.2.0/24
10.1.3.0/24

Can be summarized to
10.1.0.0/16

I'd create the following prefix list:
/routing prefix-list add prefix=10.1.0.0/16 chain=summary-route
Then I'd apply this to the interface facing the WAN under routing rip interface like this:
 
/routing rip interface interface=WAN out-prefix-list=summary-route


Again I haven't tested it but I think it's got the same effect as Cisco's interface command:
 
ip summary-address rip a.a.a.a b.b.b.b
If this work must be done to all your routers it'll reduce the routing table by reducing the routes each send to just 1 per router.

Enviado desde mi MotoE2(4G-LTE) mediante Tapatalk

Re: RIP route consolidation

Posted: Mon Oct 19, 2015 10:28 am
by tonny
Thanks, i thought along the same lines, and I tried is again with your suggestions, but ..... nope still no route summary as i would like to see it :?

Re:

Posted: Thu Oct 22, 2015 10:11 pm
by docmarius
Router 1
Routes
10.1.1.0/24
10.1.2.0/24
10.1.3.0/24

Can be summarized to
10.1.0.0/16
(...)
This statement is wrong.
You need to take in account all routes:
e.g.
10.1.1.0/24 via a
10.1.2.0/24 via a
10.1.3.0/24 via a
0.0.0.0/0 via b

Now if you summarize as you said:
10.1.0.0/16 via a
then 10.1.4.0/24, instead of going via b will go via a and this will be wrong because it is no equivalent behavior.

Since the router can not guess what you expect to happen, such summary will not happen (and should not happen) unless you enforce it some way by adding a '10.1.0.0/16 via a' route somewhere and redistribute it.

Since the PBX is the only element which has this routing table size limitation, I would choose some static routing for the PBX (the "consolidated " RIP information) if the configuration would allow that, or even a dedicated router connection to a router running RIP, as a dispatcher for the PBX, with the PBX having just a single default route to that dispatcher, and leave the routing tasks to the router.

Re: Re:

Posted: Fri Oct 23, 2015 4:56 pm
by shaoranrch
Router 1
Routes
10.1.1.0/24
10.1.2.0/24
10.1.3.0/24

Can be summarized to
10.1.0.0/16
(...)
This statement is wrong.
You need to take in account all routes:
e.g.
10.1.1.0/24 via a
10.1.2.0/24 via a
10.1.3.0/24 via a
0.0.0.0/0 via b

Now if you summarize as you said:
10.1.0.0/16 via a
then 10.1.4.0/24, instead of going via b will go via a and this will be wrong because it is no equivalent behavior.

Since the router can not guess what you expect to happen, such summary will not happen (and should not happen) unless you enforce it some way by adding a '10.1.0.0/16 via a' route somewhere and redistribute it.

Since the PBX is the only element which has this routing table size limitation, I would choose some static routing for the PBX (the "consolidated " RIP information) if the configuration would allow that, or even a dedicated router connection to a router running RIP, as a dispatcher for the PBX, with the PBX having just a single default route to that dispatcher, and leave the routing tasks to the router.
Actually my statement is not wrong at all, you gotta read carefully the original post so you'll understand why I said "can be summarized to 10.1.0.0/16" when of course, you can sumarize it to a lower prefix being more precise.

He stated that 10.X.Y.Z were the prefixes being advertised over, where X is the location's number, which means all the routes from that particular location will always have the form 10.X.Y.Z/16 - For instance:

Location 1:

10.1.0.0/16

Location 2:

10.2.0.0/16

You're not taking into account this fact and instead assuming something not related to the original request and specifications. What it means (unless the OP wants to do it a different way) is that all the addressing space from 10.1.0.0 will always belong to location 1. So there's no point on allowing the default route (0.0.0.0/0) to be taken into account for said routes when we know beforehand that they'll always point to the same place (Location's 1 routers).

It's a matter of how the addresses were schematized.

Whenever you have the possibility you should always be precise with the routes, and only use the default route as a last resource (hence the reason for it being called gateway of last resort) - Here am not letting the router guess I'm being precise with the behaviour I want.

Re: RIP route consolidation

Posted: Sat Oct 24, 2015 9:11 am
by docmarius
shaoranrch, you are absolutely right, from an functional point of view, in this particular setup, that subnet "can be summarized".
But since the routing protocols are exact, that happens only after a manual intervention by the user.

So, since a manual intervention is already needed, in this case, wouldn't it make more sense to change the architecture, provide a general P2P link to a router which "knows" about all the subnets and overcome all the issues concerning limited RIP entries in the PBX, without any summarization?
This could mean either a dedicated wire link PBX-router, or even a vlan if the PBX supports it.

Re: RIP route consolidation

Posted: Tue Oct 27, 2015 8:18 am
by Aliraza1166
MTU is everywhere set on 1542. I tryed it on various wireless links, so it has nothing to do with noise....????

Re: RIP route consolidation

Posted: Sun Oct 15, 2017 4:48 pm
by ahmadzai
i have same problem and cant do route summarization for RIPV2 in my Mikrotik CCR 1036. i have 3750 six switch's and connected each separate with 6 ports of Mikrotik and did the RIPV2 routing and everything is working normal just when i go to my cisco switch and gave (show ip route) command its routing table is showing all my /30 and /29 subnets and there total count is more than 250 subnets.
i have total four /24 subnets which total is /22 one subnet.

is there any one who can help me.