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AFAIK Local link addresses are addresses that can only talk to devices within its own subnet. Routers will not forward packets that come from local link addresses. Local link addresses are defined in the address block 169.254.0.0/16.

Cisco says the following about the L code when using show ip route. "Identifies that this is a link local route. Link local routes are automatically created when an interface is configured with an IP address and activated.".

Here's an example output of me using show ip route in a packet tracer excercise.

 10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks
C       10.10.1.0/30 is directly connected, Serial0/0/0
L       10.10.1.2/32 is directly connected, Serial0/0/0
C       10.10.1.8/30 is directly connected, Serial0/0/1
L       10.10.1.9/32 is directly connected, Serial0/0/1
D       10.10.1.16/28 [90/2170112] via 10.10.1.10, 02:09:24, Serial0/0/1

My question is: The ip adresses mentioned in show ip route are the addresses of the NICs in each route, right? Then why do the L routes show ip addresses that arent in the address block previously mentioned? Clearly 10.10.1.2/32 is not in the address block 169.254.0.0/16. Or does local link have multiple definitions?

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The L stands for local, meaning the address of the interface of the router itself within the subnet. It is unrelated to the concept of link-local addressing which indeed uses special addresses.

  • Cisco added local routes to IPv4 when they introduced Multi-Topology Routing. AFAIK, that's all it's really there for. – Dave in Ohio Mar 20 '15 at 21:12
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/32 means full subnet mask. Those are the address you put on the interfaces. so yes you are right on the first part. but i'm sry you are wrong on the second part. Network with ID 10.10.1.8/30 has 4 adresses a IPv4 has 32 bits. So 2 bits left(32-30=2) 2^2 = 4 combinations equals 4 addresses in IPv4 space.

  1. 10.10.1.8 = Network ID
  2. 10.10.1.9 = Host#1 (Your Device)
  3. 10.10.1.10 = Host#2
  4. 10.10.1.11 = Broadcast ID

The first subnet is the Same

  1. 10.10.1.0 = Network ID
  2. 10.10.1.1 = Host#1
  3. 10.10.1.2 = Host#2 (Your Device)
  4. 10.10.1.3 = Broadcast ID

On your last question you are correct. i don't know a 100% why it places a L there.. but i know that we netwerk engineers use /30 adressen in IPv4 to create peer 2 peer connection between 2 devices..

  • Nice to know about the /30 prefix and p2p. But really my question is about the L code. Thanks though, the packet tracer scenario that I'm trying to understand makes a bit more sense now. – user1534664 Mar 20 '15 at 17:08
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    Since the prefix on the L codes is /32 I'm thinking they might just be ip addresses of the network interfaces on the router. So L stands for local, and not local link? I'm going to test some stuff out. – user1534664 Mar 20 '15 at 17:10
  • As you can see in my little list i made the /32's are the ip addresses on the interfaces. In this case 10.10.1.9 on serial0/0/1 and 10.10.1.2 on serial0/0/0 – TheSec Mar 20 '15 at 17:12
  • it does, but they are 2 different subnets. To make 2 device talk using IP, they both need to have a IP address in the same subnet or they need to know a gateway to send packets to, that don't belong to the local subnet. – TheSec Mar 20 '15 at 17:27
  • It seems I don't understand properly what a subnet is then. I'll be doing some research. Thanks. – user1534664 Mar 20 '15 at 17:32

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