EIGRP convergence

[Steve Coady]

All

Network is mid-to-large

Current network has statically define default gateway pointing to inside interface of ASA.

I want to route all browsing traffic out a different path to go through a different ASA. 

Eigrp is advertising these alternate 0.0.0.0/0 paths and notes them as External, making the ad 170 for these alternate routes.

I think by changing the current static default route ad to 180+, then the eigrp alternate routes will be used. 

I am trying to determine what the convergence time would be.

The sh ip eigrp (AS#) interfaces detail command displays the interfaces with: 

Hello-interval is 5, Hold-time is 15

Can is anticipate the convergence to be 15 seconds? 

[Jon Marshall]

Steve

It's not clear what you are asking.

The timers are to do with EIGRP neighbors not route convergence.

You say you are currently using a static default route but is that being redistributed into EIGRP and are you saying you want to redistribute a different static route ?

Jon

[Steve Coady]

Jon

Thank you for the response. 

I appreciate the clarification on convergence. 

There is currently a static default gateway route that is not redistributed into eigrp. I want to force traffic to use a different default gateway and I want eigrp to determine best 0.0.0.0/0 path. 

[Jon Marshall · Accepted solution]

If the router(s) with the static default route also have an EIGRP default route in the topology table then increasing the AD of the static route to > 170 would mean the router would then use the EIGRP route.

This would be almost instantaneous.

The confusion I have is that in a mid to large network you may have a static route but how are you currently propagating that to the other routers ?

Jon

[Steve Coady]

Jon

The current topo is such that all of the routers are connected to the (2) 6509 Core switch's.

A little background:

My company, "A", purchased another company, "B", that is located in a in a city approx 40 miles away. Company "B" has it's own 100M internet link.

I have a (2) links reaching from my company to theirs

The goal is to merge as much of Company "B" into my company. Their vpn's will be built on my ASA, etc.. and then get rid of their internet pipe. 

[Jon Marshall]

Okay, that makes sense.

Jon

[Richard Burts]

If I am understanding this post correctly there are some flaws in the logic. The major flaw is that if you want to route browsing traffic out a different interface you do not use a different default route but you need to use Policy Based Routing.

There also seems to be a belief that convergence time has some relationship to hello interval or hold time. These timers would play a role if the event causing convergence were some neighbor who stops responding. But the timers would play no role in determining convergence if an interface went down or some other event such as this which can be detected immediately when it happens.

HTH

Rick

[Steve Coady]

Rick

Thank you for the response. 

I appreciate the clarification on convergence. 

If the alternate 0.0.0.0/0 routes are all ready in the eigrp topology table, why would I need to use PBR? If the static default were removed or AD changed to be higher than eigrp external AD wouldn't the alternate routes automatically select the next best 0.0.0.0/0 path? 

[Richard Burts · Accepted solution]

In your original post you indicated that you wanted certain traffic (browsing ) to go out a different path. If you want some traffic (not browsing) to use one path and browsing traffic to use a different path then you can not use a static default route and an alternate static default route to accomplish this. If you want to make routing decisions based on what type of traffic it is then you need PBR. Normal routing using static default route looks only at the destination address and not the type of traffic.

Or did I misunderstand your original requirements about routing based on type of traffic?

HTH

Rick

[Steve Coady]

Richard

Thank you for the reply. My description was not as specific as I should have made it. 

The my company, "A", purchased another company, "B". Company "B" has a 6509 as the core connected to a ASA5555x. The 6509 Core device has a static default route pointing to the inside address of the ASA as well as many ip route statements defining various egress interfaces for specific destinations, mostly for vpn peers.

My goal is to migrate everything off their ASA5555x and and discontinue their 100M internet link. Company "A" has dual Gig internet links. One as primary, the second as failover. 

The first step was to have any internet access, that was not specifically defined by ip route statements, to start using the company "A" gig links. 

[Richard Burts]

Thanks for the additional explanation. The description here is significantly different from what I understood in the original post. If you need to route some type of traffic (browsing or whatever) differently than other traffic then you would need PBR. If the requirement is simply to stop using one default route and begin using a different default route then there would not seem to be any need for PBR.

HTH

Rick