Originator_ID

The Originator_ID attribute is four bytes long and is generated by an RR. It carries the router ID of the route originator in the local AS.

• When a route is reflected by an RR for the first time, the RR adds the Originator_ID to this route. If a route already carries the Originator_ID attribute, the RR does not create a new one.

• After receiving the route, a BGP speaker checks whether the Originator_ID is the same as its router ID. If Originator_ID is the same as its router ID, the BGP speaker discards this route.

The following example shows how Originator_ID is used during BGP route selection. In Figure 1, an IBGP peer relationship is established between each two neighboring devices in AS 65001. The router IDs of Switch B and Switch C are 2.2.2.9 and 3.3.3.9, respectively, and they function as RRs. Switch D is a client of Switch B, and Switch E is a client of Switch C. Switch D and Switch E are configured to import the route 10.1.4.0/30 to BGP.

Figure 1 Networking diagram with Originator_ID configurations

Run the display bgp routing-table [ ip-address ] command on Switch A to check the configurations.

# Display the routing table of Switch A.

[HUAWEIA] display bgp routing-table

 BGP Local router ID is 10.1.3.1
 Status codes: * - valid, > - best, d - damped,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete


 Total Number of Routes: 2
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

 *>i  10.1.4.0/30        10.1.5.2        0          100        0      i
 * i                     10.1.2.2        0          100        0      i

The preceding command output shows that two routes 10.1.4.0/30 are available in the routing table of Switch A and that Switch A selects the route learned from Switch C.

[HUAWEIA] display bgp routing-table 1.1.1.9

 BGP local router ID : 10.1.3.1
 Local AS number : 65001
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 10.1.4.0/30:
 From: 10.1.3.2 (3.3.3.9)
 Route Duration: 00h00m01s
 Relay IP Nexthop: 10.1.3.2
 Relay IP Out-Interface: GigabitEthernet0/0/1
 Original nexthop: 10.1.5.2
 Qos information : 0x0
 AS-path Nil, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, best, select, pre 255, IGP cost 2
 Originator:  10.1.4.1
 Cluster list: 0.0.0.3
 Not advertised to any peer yet

 BGP routing table entry information of 10.1.4.0/30:
 From: 10.1.1.2 (2.2.2.9)
 Route Duration: 00h00m17s
 Relay IP Nexthop: 10.1.1.2
 Relay IP Out-Interface: GigabitEthernet0/0/0
 Original nexthop: 10.1.2.2
 Qos information : 0x0
 AS-path Nil, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, pre 255, IGP cost 2, not preferred for router ID
 Originator:  10.1.4.2
 Cluster list: 0.0.0.2
 Not advertised to any peer yet

The preceding command output shows that the route learned from Switch B is not selected due to a router ID issue. In fact, the router ID of Switch B is 2.2.2.9, smaller than that (3.3.3.9) of Switch C. The route learned from Switch B should be selected if the router IDs are used to determine the optimal route. However, the routes carry Originator_ID attributes. In this situation, the Originator_ID attributes (rather than router IDs) are compared. Switch A selects the route learned from Switch C because its Originator_ID (10.1.4.1) is smaller than that (10.1.4.2) of the route learned from Switch B.

Table 1 describes the attribute comparison of the routes learned from Switch B and Switch C.

If routes carry Originator_ID attributes, the Originator_ID attributes (rather than router IDs) are compared.