[LARTC] Best setup for redundant routers.

[LARTC] Best setup for redundant routers.

[Shane McKinley]

I am setting up 2 Vyatta routers that will serve as redundant failover
core routers out to the backbone of our ISP. They will be serving for
routing between other branches and the ISP and bandwidth management.

I am trying to differentiate between the plethora of information about
having redundant, automatic failover routers and pretty much decided on
VRRP for the IP address failover mechanism.

I am having a bit of a problem sorting out what will work best for
automatic routing propagation between the two units and have been
looking at the possibility of using OSPF to accomplish this to avoid
having to enter routes into two different routers.

Would OSPF work well for this? Are there better options?

Thanks for any info,

Shane McKinley
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Re: [LARTC] Best setup for redundant routers.

[Grant Taylor]

This looks to be a general routing related question rather than a "Linux 
Advanced Routing and Traffic Control" (a.k.a. LARTC) question and thus 
may be better answered elsewhere.

On 12/06/07 10:43, Shane McKinley wrote:
> I am setting up 2 Vyatta routers that will serve as redundant 
> failover core routers out to the backbone of our ISP. They will be 
> serving for routing between other branches and the ISP and bandwidth 
> management.

Ok...

> I am trying to differentiate between the plethora of information 
> about having redundant, automatic failover routers and pretty much 
> decided on VRRP for the IP address failover mechanism.

VRRP is a good idea.  I don't think I'd rely on one virtual redundant 
router through.  I would make router B be redundant for router A *AND 
router A be redundant for router B.  This way, your branch offices can 
see two different routers that have the same capabilities.  This way you 
could route some load through one router and the rest through the other 
while having both be redundant for each other.

> I am having a bit of a problem sorting out what will work best for 
> automatic routing propagation between the two units and have been 
> looking at the possibility of using OSPF to accomplish this to avoid 
> having to enter routes into two different routers.

Yes, an interior routing protocol would be good.  Based on my limited 
experience I would recommend that you use either (preferably) OSPF or 
possibly Interior BGP (a.k.a. IBGP).

> Would OSPF work well for this? Are there better options?

You could look at things like RIP or ISIS, but neither of them will be 
as good or bandwidth friendly as either OSPF or IBGP.

> Thanks for any info,

You are welcome.



Grant. . . .
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Re: [LARTC] Best setup for redundant routers.

[Grant Taylor]

On 12/6/2007 11:40 AM, Shane McKinley wrote:
> Wouldn't the redundant VRRP cause an IP address conflict?

No.  Let me try to explain using pseudo IP addresses.  For the sake of 
discussion we will use the RFC test network of 192.0.2.0/24.  (All IPs 
below will be just the last octet in said subnet.)

Real routers A and B (RA and RB respectively) and virtual routers A and 
B (VA and VB respectively) will make up the routers of the network.

Have RA be primary for VA's IP and backup for VB's IP.  Then have RB be 
backup for VA's IP and primary for VB's IP.  So you would have four IPs 
in use (RA, RB, VA, and VB).  You would only have clients use VA and / 
or VB as their default gateway(s).

So, if you have the following IPs used:

VA = .254
VB = .253
RA = .252
RB = .251

Real router A would have it's ""management IP of .252 and participate 
(as the primary) in the VRRP virtual router A IP / MAC address of .254 
and (as the secondary) in the VRRP virtual router B IP / MAC address of 
.253.

Real router B would have it's ""management IP of .251 and participate 
(as the secondary) in the VRRP virtual router A IP / MAC address of .254 
and (as the primary) in the VRRP virtual router B IP / MAC address of .253.

As you can see there are four IP addresses used, two are what clients 
would use as potential default gateways and two are for management of 
the real routers.

With the two different IPs that you can hand out to clients, you could 
do some load balancing by having some clients use one virtual router and 
others use the other virtual router.

Heck, if you wanted to you could even add a third real router (RC) to be 
a tertiary router for virtual routers.

> If not, that would be sweet. I would have redundancy for my redundancy.

Start thinking about how sweet things can be....



Grant. . . .
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Re: [LARTC] Best setup for redundant routers.

[Mohan Sundaram]

Grant Taylor wrote:
> This looks to be a general routing related question rather than a "Linux 
> Advanced Routing and Traffic Control" (a.k.a. LARTC) question and thus 
> may be better answered elsewhere.
*nod*
> 
> On 12/06/07 10:43, Shane McKinley wrote:
>> I am setting up 2 Vyatta routers that will serve as redundant 
>> failover core routers out to the backbone of our ISP. They will be 
>> serving for routing between other branches and the ISP and bandwidth 
>> management.
Would be interesting to know how they perform.
> Yes, an interior routing protocol would be good.  Based on my limited 
> experience I would recommend that you use either (preferably) OSPF or 
> possibly Interior BGP (a.k.a. IBGP).
Either is good. For just 2 routers, most dynamic protocols work well. 
Older protocols failed in scaling to larger networks. AFAIR, OSPF 
support discovered route cost propogation which is useful in route 
selection/ load balancing/ECMP etc. Do not remember if IBGP does it. Has 
been a while and so a little rusty on finer details.
> You could look at things like RIP or ISIS, but neither of them will be 
> as good or bandwidth friendly as either OSPF or IBGP.
For just 2 routers, the decision is pretty simple - any. I'd go with 
OSPF or IBGP depending on comfort, skillset and support at locations needed.

Mohan
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