IS-IS and OSPF comparison
1) IS-IS defines only two types of network topologies: broadcast and general topology.Cisco router link into point-to-point and broadcast.
OPSF defines five network types: point-to-point and point-to-multipoint, broadcast and NBMA, as well as virtual links
OPSF defines five network types: point-to-point and point-to-multipoint, broadcast and NBMA, as well as virtual links
2) Both protocols maintain a link state database (Link State Database)
IS-IS LSP (Link State PDU), the LSP is a datagram;
OSPF uses LSA (Link State Advertisements), the LSA must be encapsulated (encapsulate ) in the OSPF header and IP header.
IS-IS LSP (Link State PDU), the LSP is a datagram;
OSPF uses LSA (Link State Advertisements), the LSA must be encapsulated (encapsulate ) in the OSPF header and IP header.
3) Both protocols use the SPF algorithm to calculate the routing
IS-IS routing domain (intra-area) run Level 1 SPF calculation routing inter-domain (inter-area) run Level 2 SPF;
OSPF domain (intra- area) running the SPF calculation routing, distance vector algorithm run between domains (inter-area) (distance vector algorithm) to calculate the route.
IS-IS routing domain (intra-area) run Level 1 SPF calculation routing inter-domain (inter-area) run Level 2 SPF;
OSPF domain (intra- area) running the SPF calculation routing, distance vector algorithm run between domains (inter-area) (distance vector algorithm) to calculate the route.
4) Both agreements to create a two-tier hierarchical network topology
IS-IS backbone is not specific to a domain using the domain (area) , but by the continuous Level 2 routers;
OSPF backbone must have and must area 0;
IS-IS domain boundary on the link between the router (link);
OSPF domain border router;
IS-IS two-tier hierarchical network topology is not required, the network can be completely Level 1 router or fully constituted by Level 2 routers.
Of OSPF area 0, only one area, but it must be to area 0.
IS-IS backbone is not specific to a domain using the domain (area) , but by the continuous Level 2 routers;
OSPF backbone must have and must area 0;
IS-IS domain boundary on the link between the router (link);
OSPF domain border router;
IS-IS two-tier hierarchical network topology is not required, the network can be completely Level 1 router or fully constituted by Level 2 routers.
Of OSPF area 0, only one area, but it must be to area 0.
5) One of the IS-IS characteristics: IS-IS router can have up to three domain address (area addresses), which is useful in the inter-domain transmission.
6) The two protocols are classless routing protocols in the area between the summary (summary)
7) The two protocols handle the error (corrupted) LSP / LSA method:
any router can discard the IS-IS (purge) corrupted LSP;
sender of the LSA (originator) can be discarded only corrupted in the OSPF (purge) .
any router can discard the IS-IS (purge) corrupted LSP;
sender of the LSA (originator) can be discarded only corrupted in the OSPF (purge) .
8) In the broadcast networks (broadcast network) in the two protocols should establish
IS-IS adjacency relations , as long as the neighbor's Hello Datagram your identity, the adjacency relationship is established successfully. The stage of going through a three-way handshake process: Down → Init → Up.
OSPF, establish adjacency relations before experienced: Down → Init → Two-way → Exstart → Exchange → Uploading → Full.
IS-IS adjacency relations , as long as the neighbor's Hello Datagram your identity, the adjacency relationship is established successfully. The stage of going through a three-way handshake process: Down → Init → Up.
OSPF, establish adjacency relations before experienced: Down → Init → Two-way → Exstart → Exchange → Uploading → Full.
9) IS-IS neighbors establish adjacency relations the Hello-intervals or Hello multipliers; the
OSPF Neighbors not establish adjacency relationship if Hello-intervals or Dead-intervals.
OSPF Neighbors not establish adjacency relationship if Hello-intervals or Dead-intervals.
10) in a broadcast network (broadcast network) both protocols must select a DIS / DR
IS-IS DIS is a dynamic selection, that is, if a higher priority or greater address of the router to join the network, new router becomes the DIS; the
OSPF in DR relatively stable, that the DR no down out, the DR maintains its position;
the IS-IS broadcast network router to establish adjacency relations with all neighbors;
OSPF routers only broadcast network DR and BDR neighbor to establish adjacency relations;
IS-IS, DIS sync (synchronize) with its neighbors. DIS generates the pseudonode for the LAN, and send PSNPs (partial sequence number PDUs) every three seconds or every 10 seconds the sending CSNPs (complete sequence number PDUs). Other router can also be used PSNPs apply to DIS for missing LSP or send DIS a new LSP. Because the flood PDUs, DIS DIS does not require synchronized with its neighbors (synchronization); their neighbors because no sync (synchronization), and so no BDIS.
OSPF DR / BDR unicast (unicast) transmission DDP, respectively, with the other so the router synchronization (synchronization).
IS-IS DIS is a dynamic selection, that is, if a higher priority or greater address of the router to join the network, new router becomes the DIS; the
OSPF in DR relatively stable, that the DR no down out, the DR maintains its position;
the IS-IS broadcast network router to establish adjacency relations with all neighbors;
OSPF routers only broadcast network DR and BDR neighbor to establish adjacency relations;
IS-IS, DIS sync (synchronize) with its neighbors. DIS generates the pseudonode for the LAN, and send PSNPs (partial sequence number PDUs) every three seconds or every 10 seconds the sending CSNPs (complete sequence number PDUs). Other router can also be used PSNPs apply to DIS for missing LSP or send DIS a new LSP. Because the flood PDUs, DIS DIS does not require synchronized with its neighbors (synchronization); their neighbors because no sync (synchronization), and so no BDIS.
OSPF DR / BDR unicast (unicast) transmission DDP, respectively, with the other so the router synchronization (synchronization).
11) The two protocols have authentication (authentication)
IS-IS supports only simple authentication;
OSPF supports simple authentication and MD5 authentication.
12) IS-IS the L1/L2 router does not release L2 to L1 routers routing. L1 routers like the completely end the OSPF domain (totally stubby area).
13) ISIS protocol configuration no ip ospf network command in OSPF protocol similar to the configuration options on NBMA as "HUB" ROUTER must be configured as a point to point subinterfaces (including change of address) so that each PVC links in different SUBNET.
IS-IS supports only simple authentication;
OSPF supports simple authentication and MD5 authentication.
12) IS-IS the L1/L2 router does not release L2 to L1 routers routing. L1 routers like the completely end the OSPF domain (totally stubby area).
13) ISIS protocol configuration no ip ospf network command in OSPF protocol similar to the configuration options on NBMA as "HUB" ROUTER must be configured as a point to point subinterfaces (including change of address) so that each PVC links in different SUBNET.
