LISP - Example 1

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LISP Example 1

This is a simple example of LISP (Locator/ID Separation Protocol) configuration on Cisco routers (using Dynamips and GNS3).

Author: Christophe Fillot - 30-Jul-2010

This lab uses Cisco IOS 15.1(1)XB2, which provides MS (Map Server) and MR (Map Resolver) functions. For emulation efficiency, all routers in this lab use the same IOS release, even if they don't require LISP capabilities.


Table of contents
1 Topology
2 IOS configurations
3 Endpoint Identifiers (EID) and Routing Locators (RLOC)
4 Configuration of Map Server and Map Resolver
5 Verifying site registration (on the Map Server)
6 "lig" tool (LISP Internet Groper)
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Topology

Image:LISP_lab1.png


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IOS configurations

ISP routers

Customer 1

Customer 2


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Endpoint Identifiers (EID) and Routing Locators (RLOC)

Customer 1 uses EID 192.168.1.0/24, Customer 2 uses EID 192.168.2.0/24.

The EIDs are not known from the ISP routers that forward packets (Core1 and Core2 in this example).

The ISP forwarding routers only know how to reach RLOC (xTR1 has RLOC 10.0.0.2, xTR2 has RLOC 10.0.0.6).


xTR1 and xTR2 register their respective EIDs to the Map Server (MS), which maintains EID-to-RLOC mappings.

When xTR routers need to lookup for a specific EIDs, they ask the Map Resolver (MR).

MS and MR routers are not involved in forwarding.


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Configuration of Map Server and Map Resolver

A specific VRF (in this example "lisp_alt") is used to exchange EIDs between the Map Server and the Map Resolver.

MS and MR establish a BGP session through a GRE tunnel in this VRF. The MS sends EID information to the MR using "redistribute lisp" in BGP configuration.


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Verifying site registration (on the Map Server) 

MS#show lisp site 
LISP Site Registration Information

Site Name      Last      Up   Who Last             EID Prefix
               Register       Registered           
Customer1      00:00:04  yes  10.0.0.2             192.168.1.0/24
Customer2      00:00:38  yes  10.0.0.6             192.168.2.0/24

Detailed information: 

MS#show lisp site detail
LISP Site Registration Information

Site name: Customer1
Description: "Customer1"
Allowed configured locators: any
Allowed EID-prefixes:
  EID-prefix: 192.168.1.0/24
    First registered:     00:01:11
    Routing table tag:    0x3E8
    Origin:               Configuration
    Registration errors:  
      Authentication failures:   0
      Allowed locators mismatch: 0
    ETR 10.0.0.2, last registered 00:00:29, no proxy-reply
                  TTL 1d00h
      Locator   Local  State      Pri/Wgt
      10.0.0.2  yes    up           1/100
Site name: Customer2
Description: "Customer2"
Allowed configured locators: any
Allowed EID-prefixes:
  EID-prefix: 192.168.2.0/24
    First registered:     04:31:19
    Routing table tag:    0x7D0
    Origin:               Configuration
    Registration errors:  
      Authentication failures:   0
      Allowed locators mismatch: 0
    ETR 10.0.0.6, last registered 00:00:22, no proxy-reply
                  TTL 1d00h
      Locator   Local  State      Pri/Wgt
      10.0.0.6  yes    up           1/100

We can also check that the VRF "lisp_alt" is correctly populated: 

MS#sh ip ro vrf lisp_alt

Routing Table: lisp_alt
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, l - LISP
       + - replicated route

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.253.0.0/30 is directly connected, Tunnel0
L        10.253.0.1/32 is directly connected, Tunnel0
l     192.168.1.0/24 [10/1] via 0.0.0.0, 00:07:13, Null0
l     192.168.2.0/24 [10/1] via 0.0.0.0, 03:57:31, Null0


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"lig" tool (LISP Internet Groper)

The "lig" command allows to determine a RLOC for the specified EID: 

xTR1#lig 192.168.2.1
Mapping information for EID 192.168.2.1 from 10.0.0.6 with RTT 96 msecs
192.168.2.0/24, uptime: 04:42:25, expires: 23:59:57, via map-reply, complete
  Locator   Uptime    State      Pri/Wgt
  10.0.0.6  04:42:25  up           1/100
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