OSPF

Jan 8 2009

Redistributing ISIS into OSPF

Someone asked me recently for an example of ISIS redistribution into OSPF. So here goes.

Consider the toplogy below.

isis-into-ospf

We redistribute ISIS into OSPF and vice versa on R2. We should then be able to ping R1 loopback from R3 loopback and vice versa.

Watch the video below or alternativly click here to download and watch it on your iPod.

The Flash plugin is required to view this object.

The commands used in the above video can be found below.

R1
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface FastEthernet1/0
description :connected to R2 fa1/0:
ip address 10.0.0.1 255.255.255.252
ip ospf network point-to-point
!
router ospf 1
log-adjacency-changes
network 1.1.1.1 0.0.0.0 area 0
network 10.0.0.0 0.0.0.3 area 0
!

R2
!
interface Loopback0
ip address 2.2.2.2 255.255.255.255
!
interface FastEthernet1/0
description :connected to R1 fa1/0:
ip address 10.0.0.2 255.255.255.252
ip ospf network point-to-point
!
interface FastEthernet1/1
description :connected to R3 fa1/0:
ip address 10.0.0.5 255.255.255.252
ip router isis
!
router ospf 1
log-adjacency-changes
redistribute isis level-2 subnets
network 2.2.2.2 0.0.0.0 area 0
network 10.0.0.0 0.0.0.3 area 0
!
router isis
net 49.0001.0000.0000.0002.00
is-type level-2-only
redistribute ospf 1
!

R3
!
interface Loopback0
ip address 3.3.3.3 255.255.255.255
!
interface FastEthernet1/0
description :connected to R2 fa1/1:
ip address 10.0.0.6 255.255.255.252
ip router isis
!
router isis
net 49.0001.0000.0000.0003.00
is-type level-2-only
passive-interface Loopback0
!

By Zarar • CCIE SP, iPod, IS-IS, OSPF • 2 • Tags: , ,

Nov 29 2008

Traffic Engineering – IGP extensions (OSPF)

OSPF has been extended using TLV and sub-TLVs in order to be used with Traffic Engineering.

RFC 3630 contains details of the extensions.

The OSPF TLV extension for TE is also referred to as OSPF Opaque LSA 10. This LSA has an area flooding scope.

Opaque LSA 10 contains 2 top level TLVs.

1. Router Address TLV

2. Link TLV

Router Address TLV

If a router advertises BGP routes with the BGP next hop attribute set to the BGP router ID, then the OSPF router ID should be the same as the BGP router ID.

Link TLV

The Link TLV describes a single link. It is composed of a set of sub-TLVs.  The key sub-TLVs are:-

Sub-TLV 6 – Maximum bandwidth (4 octets)

Sub-TLV 7 – Maximum reservable bandwidth (4 octets)

Sub-TLV 8 – Unreserved bandwidth (32 octets)

By zismail • CCIE SP, OSPF, Traffic Engineering • 0 • Tags: , , ,

Nov 18 2008

OSPF Sham-Links

OSPF sham-links give the technical administrator an option to use either the back door link or the WAN link by presenting Type 1 LSAs over the WAN cloud.  CEs then have Type 1 LSAs via 2 routes and as they are the same type of LSA you can manipulate the cost to either use the back door or the WAN link.

By zismail • CCIE SP, MPLS VPN, OSPF, PE-CE Routing • 0 • Tags: , ,