Route types

[olly ahmed]

As per my thinking / study so far, directly connected routes are mainly a types of static routes. Is my thinking right ? Can anyone help ? If not please give me proper document link.

[acampbell]

Hi,

Look at this link:-
http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/8651-21.html

From the table the types of route you will see are shown along with their administritve distances

Connected 0 -- These appear because you have configured an IP addres and mask on an interface, so they belong to this router.

Static 1   -- These appear because you have configured a "STATATIC route" on your router, e.g. "ip route 1.2.3.4 255.255.255.0 NEXT-HOP"

eBGP 20  - Dynamic from the BGP routing process

EIGRP (internal)  90  - Dynamic from the EIGRP routing process 

IGRP 100  - Dynamic from the IGRP routing process

OSPF 110  - Dynamic from the OSPF routing process

IS-IS 115 - Dynamic from the IS-IS routing process

RIP 120 - Dynamic from the RIP routing process

EIGRP (external) 170  - Dynamic from the EIGRP routing process

iBGP 200  - Dynamic from the BGP routing process

EIGRP summary route 5  - Dynamic from the EIGRP routing process

Routes with the "lowest admin distance" will populate the routing table

So lets say you are running RIP and you learn a route to network 192.168.1.0/24 but you also have a static route configured for the same network "ip route 192.168.1.0 255.255.255.0 NEXT-HOP" then the STATIC route will be in the routing table as it has an admin distance of "1" which is lower than the RIP learned route of admin distance "120".

The RIP learned route will stay in the RIP database and would move pop in the routing table if you were to remove your static route to the same network.

Try to obtain a couple of routers & switches so you can build a wee lab and test (learn) to prove the theories you learn to yourself.

Hope this helps
Regards
Alex

[Richard Burts · Accepted solution]

Thinking about the types of routes can be an interesting exercise. And if you want to simplify things and get down to two categories of routes there are dynamic routes and non-dynamic routes. And in that sense connected routes and static routes are both in the same category and you might think of them as the same type of route. But as you look a bit deeper there are some interesting differences. The first difference is how they are created with static routes using the ip route command while connected routes use the interface x/ip address commands. Another interesting difference is about administrative distance. A connected route is the only type of route whose administrative distance can not be changed. A connected route is always preferred over any other type of route for the same prefix.

HTH

Rick

[Richard Burts]

I am glad that my suggestion was helpful. Thank you for using the rating system to mark this question as answered. This will help other readers in the forum to identify discussions that have helpful information.

HTH

Rick

[meh000001]

Thanks for your helpful information. I have another question: Which one is faster? Static route or Dynamic route?

[Richard Burts]

Your question is not clear to me. Are you talking about faster in terms of leaning the route, faster in terms of converging, or faster in terms of forwarding IP packets?

In terms of learning the route it might be argued that static routes are faster since they are processed as soon as configured and have no need to find neighbors and to advertise routes. But it is not an important difference in speed.

In terms of convergence clearly dynamic routes converge faster than static routes.

In terms of forwarding IP packets there is absolutely no difference in speed between static or dynamic routes. Forwarding IP packets uses the contents of the layer 3 forwarding table and it makes no difference in forwarding performance whether the route was learned from static or from dynamic.

HTH

Rick

[Joseph W. Doherty]

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Posting

Once a route is in the route table, lookup should be the same regardless of how it got there.  I.e. for packet forwarding, it shouldn't matter.

As to getting a route into the route table, static might be faster because it's already known directly on the router while many dynamic routes are coming from the protocol.  Those in the protocol known to the router (i.e. in the local configuration) might be about the same "speed" as a static, but those that are dynamically learned will likely take longer to obtain.

[edit]

PS:

Didn't see Rick's new posting until after I posted above, but I believe the above also confirms what Rick wrote.