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New Member

what is the difference between local route (L) and directly connected (C)?

I am reviewing the v2 release of ICND1 course materials. Looking at the student guide pg. 2-67 and 2-68, there is a screenshot of a routing table; some routes are marked with a C (directly connected) others with an L (local route). The explanation is unhelpful. C is defined as referring to directly connected networks, whereas L is defined as referring to "local routes and local interfaces within connected networks". So what's the difference, please? Thanks for any advice on this.

  • LAN Switching and Routing
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Cisco Employee

Re: what is the difference between local route (L) and directly

Thanks for the update. Happy to help you.

Could you please mark the thread as answered so that we dont leave the thread as not answered.

Thanks in advance.

Regards

Inayath

*Plz rate all usefull posts.

6 REPLIES
Cisco Employee

what is the difference between local route (L) and directly conn

Recent versions of the IOS software started displaying these local prefixes in the IPv4 routing table. As far as I know, this was always the case with IPv6 routing table and IPv6 addresses, and now it has been also adopted for the IPv4 routing table.

These entries do not basically tell you anything new as they merely state an obvious fact: your own IP address is reachable on a particular interface. Having this route in a routing table merely makes sure that the packet destined for your IP address will not be rerouted but rather processed locally. I believe that these entries were in the routing table even before they started being displayed, they just were hidden.

This is my idea about this.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080c14371.shtml

Ref:https://supportforums.cisco.com/thread/2040438

HTH

Regards

Inayath

********* Plz rate if this info is helpfull*****************

New Member

Re: what is the difference between local route (L) and directly

Thanks for the link. It appears there are several things going on with L routes. I summarize from the link you provided:

"1. when you configure "redistribute connected" under any routing process, the connected routes are redistributed, but the local routes are not.

2. The local entries are needed by the MTR feature. In MTR, one interface/IP address can belong to multiple topologies. If one topology is not enabled on one interface in MTR, that connected route is not present in that topology. However, the packets destined to that IP address must still be processed by the router that owns the IP address, even if that topology is not enabled on that interface. This is why local host routes are present in all topologies, even if the topology is disabled.

3. It is normal for local host routes to be listed in the IPv4 and IPv6 routing table for IP addresses of the router's interfaces. Their purpose is to create a corresponding CEF entry as a receive entry so that the packets destined to this IP address can be processed by the router itself. These routes cannot be redistributed into any routing protocol."

    
Redistributuion, MTR, and the differences between CEF-processing and the other two sorts of packet processing are way beyond what ICND1 students need to know however.

Cheers,

FW

Cisco Employee

Re: what is the difference between local route (L) and directly

Flash,

Are there any question for me on this ?

New Member

Re: what is the difference between local route (L) and directly

No further questions, thank you. The link you provided told me what I needed to know. "The case is solv-ed," as Inspector Clouseau would say.

Cheers,

FW

Cisco Employee

Re: what is the difference between local route (L) and directly

Thanks for the update. Happy to help you.

Could you please mark the thread as answered so that we dont leave the thread as not answered.

Thanks in advance.

Regards

Inayath

*Plz rate all usefull posts.

New Member

what is the difference between local route (L) and directly conn

My web interface doesn't seem to link to the rating applet. Anyway, 5 stars! Thanks,

FW

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