BGP-4 Aggregation
- Tracy Yang (Unlicensed)
Command References
admin@XorPlus# set protocols bgp aggregate network6 <IPV6-Network>
Note: This command is used to set IPv6 route aggregation. Routes with different MED values should not be aggregated.
admin@XorPlus# set protocols bgp aggregate network6 <IPV6-Network> suppress-detail <true/false>
Note: This command is used to enable or disable suppress-detail BGP route entry. The detail BGP route entry is suppressed by default.
admin@XorPlus# set protocols bgp aggregate network6 <IPV6-Network> brief-mode <true/false>
Note: This command is used to create AS_SET when the BGP route entry has a different AS_PATH before aggregation.
The following examples demonstrate different methods of aggregation that are seen on the internet. The way aggregates are formed and advertised, and whether they carry more-specific routes with them will influence traffic patterns and sizes of BGP routing tables. Remember that aggregation applies to routes that exist in the BGP routing table. An aggregate can be sent if at least one more specific route of that aggregate exists in the BGP table.
Route aggregation at border or core routers can also reduce the potential unpleasant side effects associated with IGP injection into BGP. With aggregation, multiple route entries are injected into BGP as a summary aggregate. Single route instability in any single element of the aggregate does not affect the stability of the aggregate itself.
IPv6 BGP only supports manual aggregation. Auto-summary is only for IPv4 BGP.
Aggregate Only, Suppressing the More-Specific By Default
Note: The specific route entry will be suppressed after configuring route aggregation by default.
Figure 1-22
Step 1: Configure BGP as topo showed
Switch A:
admin@XorPlus# set protocols bgp bgp-id 33.33.33.33 admin@XorPlus# set protocols bgp local-as 10 admin@XorPlus# set protocols bgp peer 5005::1 local-ip 5005::2 admin@XorPlus# set protocols bgp peer 5005::1 as 9 admin@XorPlus# set protocols bgp peer 5005::1 ipv6-unicast true
Switch B:
admin@XorPlus# set protocols bgp bgp-id 9.9.9.9 admin@XorPlus# set protocols bgp local-as 9 admin@XorPlus# set protocols bgp peer 6006::2 local-ip 6006::1 admin@XorPlus# set protocols bgp peer 6006::2 as 9 admin@XorPlus# set protocols bgp peer 6006::2 next-hop-self true admin@XorPlus# set protocols bgp peer 6006::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 3003::1 local-ip 3003::2 admin@XorPlus# set protocols bgp peer 3003::1 as 6 admin@XorPlus# set protocols bgp peer 3003::1 ipv6-unicast true admin@XorPlus# set protocols bgp peer 5005::2 local-ip 5005::1 admin@XorPlus# set protocols bgp peer 5005::2 as 10 admin@XorPlus# set protocols bgp peer 5005::2 ipv6-unicast true
Switch C:
admin@XorPlus# set protocols bgp bgp-id 44.44.44.44 admin@XorPlus# set protocols bgp local-as 12 admin@XorPlus# set protocols bgp peer 2002::1 local-ip 2002::2 admin@XorPlus# set protocols bgp peer 2002::1 as 9 admin@XorPlus# set protocols bgp peer 2002::1 ipv6-unicast true
Switch D:
admin@XorPlus# set protocols bgp bgp-id 26.26.26.26 admin@XorPlus# set protocols bgp local-as 9 admin@XorPlus# set protocols bgp peer 1001::1 local-ip 1001::2 admin@XorPlus# set protocols bgp peer 1001::1 as 6 admin@XorPlus# set protocols bgp peer 1001::1 ipv6-unicast true admin@XorPlus# set protocols bgp peer 2002::2 local-ip 2002::1 admin@XorPlus# set protocols bgp peer 2002::2 as 12 admin@XorPlus# set protocols bgp peer 2002::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 6006::1 local-ip 6006::2 admin@XorPlus# set protocols bgp peer 6006::1 as 9 admin@XorPlus# set protocols bgp peer 6006::1 next-hop-self true admin@XorPlus# set protocols bgp peer 6006::1 ipv6-unicast true
Switch E:
admin@XorPlus# set protocols bgp bgp-id 6.6.6.6 admin@XorPlus# set protocols bgp local-as 6 admin@XorPlus# set protocols bgp peer 1001::2 local-ip 1001::1 admin@XorPlus# set protocols bgp peer 1001::2 as 9 admin@XorPlus# set protocols bgp peer 1001::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 3003::2 local-ip "3003::1" admin@XorPlus# set protocols bgp peer 3003::2 as 9 admin@XorPlus# set protocols bgp peer 3003::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 4004::2 local-ip 4004::1 admin@XorPlus# set protocols bgp peer 4004::2 as 100 admin@XorPlus# set protocols bgp peer 4004::2 ipv6-unicast true
Switch F:
admin@XorPlus# set protocols bgp bgp-id 100.100.100.100 admin@XorPlus# set protocols bgp local-as 100 admin@XorPlus# set protocols bgp peer 4004::1 local-ip 4004::2 admin@XorPlus# set protocols bgp peer 4004::1 as 6 admin@XorPlus# set protocols bgp peer 4004::1 ipv6-unicast true
Step 2: Switch A propagate BGP route entry 9999::/64 to Switch B. Switch C propagate BGP route entry 9999:0:0:1::/64 to Switch D.
Note: Check BGP route table on Switch E. There should be two BGP route entries from a different AS-path.
Switch E:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999:0:0:1::/64 3003::2 9.9.9.9 9 12 i *> 9999::/64 1001::2 26.26.26.26 9 10 i * 9999:0:0:1::/64 1001::2 26.26.26.26 9 12 i admin@XorPlus#
Switch F:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999:0:0:1::/64 4004::1 6.6.6.6 6 9 12 i *> 9999::/64 4004::1 6.6.6.6 6 9 10 i admin@XorPlus#
Step 3: Configure route aggregation on Switch E
Note: The specific route entry was suppressed by default. User can cancel suppress specific routes by command set protocols bgp aggregate network6 <IPV6-Network> suppress-detail false
Switch E:
admin@XorPlus# set protocols bgp aggregate network6 9999::/40
Check BGP route table on Switch F:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999::/40 4004::1 6.6.6.6 6 i admin@XorPlus# admin@XorPlus# run show bgp routes ipv6 detail 9999::/40 From peer: 6.6.6.6 Route: Winner Origin: IGP AS Path: 6 Nexthop: 4004::1 Multiple Exit Discriminator: 0 Local Preference: 100 Aggregator: 6.6.6.6
Note: We can see the aggregated IPv6 network 9999::/40 on Switch F. Aggregator 6.6.6.6 created this aggregated network. The AS-path is the AS number that created this aggregated network.
Step 4: Disable suppress-detail
Note: In some cases, more-specific routes, in addition to the aggregate, need to be passed (leaked) to a neighboring AS. This is usually done in AS's multihomed to a single provider. An AS (the provider) that gets the more-specific routes would be able to make a better decision about which way to reach the route.
Switch E:
admin@XorPlus# set protocols bgp aggregate network6 9999::/40 suppress-detail false
Check the BGP route table on Switch F:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999::/40 4004::1 6.6.6.6 6 i *> 9999:0:0:1::/64 4004::1 6.6.6.6 6 9 12 i *> 9999::/64 4004::1 6.6.6.6 6 9 10 i admin@XorPlus# admin@XorPlus# run show bgp routes ipv6 detail 9999::/40 From peer: 6.6.6.6 Route: Winner Origin: IGP AS Path: 6 Nexthop: 4004::1 Multiple Exit Discriminator: 0 Local Preference: 100 Aggregator: 6.6.6.6 9999::/64 From peer: 6.6.6.6 Route: Winner Origin: IGP AS Path: 6 9 10 Nexthop: 4004::1 Multiple Exit Discriminator: 0 Local Preference: 100 9999:0:0:1::/64 From peer: 6.6.6.6 Route: Winner Origin: IGP AS Path: 6 9 12 Nexthop: 4004::1 Multiple Exit Discriminator: 0 Local Preference: 100
Note: The specific route entry did not suppress after disable suppress-detail.
Loss of Information Inside Aggregates
Aggregation causes loss of granularity. The detailed information that exists in the specific prefixes will be lost when summarized in the form of aggregates. The purpose of an AS_SET is to attempt to preserve the attributes carried in the specific routes in a mathematical SET that gives a better idea of the elements of the aggregate.
Note: This example demonstrates how to create as_set when the as_path is different before the BGP route entry was aggregated. It will not create as_set by default.
Figure 1-23
Step 1: Configure BGP as topo showed
Switch A:
admin@XorPlus# set protocols bgp bgp-id 33.33.33.33 admin@XorPlus# set protocols bgp local-as 10 admin@XorPlus# set protocols bgp peer 5005::1 local-ip 5005::2 admin@XorPlus# set protocols bgp peer 5005::1 as 9 admin@XorPlus# set protocols bgp peer 5005::1 ipv6-unicast true
Switch B:
admin@XorPlus# set protocols bgp bgp-id 9.9.9.9 admin@XorPlus# set protocols bgp local-as 9 admin@XorPlus# set protocols bgp peer 6006::2 local-ip 6006::1 admin@XorPlus# set protocols bgp peer 6006::2 as 9 admin@XorPlus# set protocols bgp peer 6006::2 next-hop-self true admin@XorPlus# set protocols bgp peer 6006::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 3003::1 local-ip 3003::2 admin@XorPlus# set protocols bgp peer 3003::1 as 6 admin@XorPlus# set protocols bgp peer 3003::1 ipv6-unicast true admin@XorPlus# set protocols bgp peer 5005::2 local-ip 5005::1 admin@XorPlus# set protocols bgp peer 5005::2 as 10 admin@XorPlus# set protocols bgp peer 5005::2 ipv6-unicast true
Switch C:
admin@XorPlus# set protocols bgp bgp-id 44.44.44.44 admin@XorPlus# set protocols bgp local-as 12 admin@XorPlus# set protocols bgp peer 2002::1 local-ip 2002::2 admin@XorPlus# set protocols bgp peer 2002::1 as 9 admin@XorPlus# set protocols bgp peer 2002::1 ipv6-unicast true
Switch D:
admin@XorPlus# set protocols bgp bgp-id 26.26.26.26 admin@XorPlus# set protocols bgp local-as 9 admin@XorPlus# set protocols bgp peer 1001::1 local-ip 1001::2 admin@XorPlus# set protocols bgp peer 1001::1 as 6 admin@XorPlus# set protocols bgp peer 1001::1 ipv6-unicast true admin@XorPlus# set protocols bgp peer 2002::2 local-ip 2002::1 admin@XorPlus# set protocols bgp peer 2002::2 as 12 admin@XorPlus# set protocols bgp peer 2002::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 6006::1 local-ip 6006::2 admin@XorPlus# set protocols bgp peer 6006::1 as 9 admin@XorPlus# set protocols bgp peer 6006::1 next-hop-self true admin@XorPlus# set protocols bgp peer 6006::1 ipv6-unicast true
Switch E:
admin@XorPlus# set protocols bgp bgp-id 6.6.6.6 admin@XorPlus# set protocols bgp local-as 6 admin@XorPlus# set protocols bgp peer 1001::2 local-ip 1001::1 admin@XorPlus# set protocols bgp peer 1001::2 as 9 admin@XorPlus# set protocols bgp peer 1001::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 3003::2 local-ip "3003::1" admin@XorPlus# set protocols bgp peer 3003::2 as 9 admin@XorPlus# set protocols bgp peer 3003::2 ipv6-unicast true admin@XorPlus# set protocols bgp peer 4004::2 local-ip 4004::1 admin@XorPlus# set protocols bgp peer 4004::2 as 100 admin@XorPlus# set protocols bgp peer 4004::2 ipv6-unicast true
Switch F:
admin@XorPlus# set protocols bgp bgp-id 100.100.100.100 admin@XorPlus# set protocols bgp local-as 100 admin@XorPlus# set protocols bgp peer 4004::1 local-ip 4004::2 admin@XorPlus# set protocols bgp peer 4004::1 as 6 admin@XorPlus# set protocols bgp peer 4004::1 ipv6-unicast true
Step 2: Switch A propagate BGP route entry 9999::/64 to Switch B. Switch C propagate BGP route entry 9999:0:0:1::/64 to Switch D.
Note: Check BGP route table on Switch E. There should be two BGP route entries from different as-path.
Switch E:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999:0:0:1::/64 3003::2 9.9.9.9 9 12 i *> 9999::/64 1001::2 26.26.26.26 9 10 i * 9999:0:0:1::/64 1001::2 26.26.26.26 9 12 i admin@XorPlus#
Switch F:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999:0:0:1::/64 4004::1 6.6.6.6 6 9 12 i *> 9999::/64 4004::1 6.6.6.6 6 9 10 i admin@XorPlus#
Step 3: Configuure Route aggregation on Switch E
Note: The BGP speaker will not create AS_SET by default. User can enable the BGP speaker to create AS_SET via command set protocols bgp aggregate network6 <IPV6-Network> brief-mode false
Switch E:
admin@XorPlus# set protocols bgp aggregate network6 9999::/40
Check BGP route table on Switch F:
admin@XorPlus# run show bgp routes ipv6 Status Codes: * valid route, > best route Origin Codes: i IGP, e EGP, ? incomplete Prefix Nexthop Peer AS Path ---------------------------- ------------------------ --------------- ------------ *> 9999::/40 4004::1 6.6.6.6 6 i admin@XorPlus# admin@XorPlus# run show bgp routes ipv6 detail 9999::/40 From peer: 6.6.6.6 Route: Winner Origin: IGP AS Path: 6 Nexthop: 4004::1 Multiple Exit Discriminator: 0 Local Preference: 100 Aggregator: 6.6.6.6
Note: The aggregated IPv6 network 9999::/40 on Switch F. Aggregator 6.6.6.6 created this aggregated network. The as-path is the AS number that created this aggregated network.
Step 4: Create AS_SET
Note: It will not Create AS_SET by default.
Switch E:
admin@XorPlus# set protocols bgp aggregate network6 9999::/40 brief-mode false
Check the BGP route table on Switch F:
admin@XorPlus# run show bgp routes ipv6
Status Codes: * valid route, > best route
Origin Codes: i IGP, e EGP, ? incomplete
Prefix Nexthop Peer AS Path
---------------------------- ------------------------ --------------- ------------
*> 9999::/40 4004::1 6.6.6.6 6 {9 10} i
admin@XorPlus#
admin@XorPlus# run show bgp routes ipv6 detail
9999::/40
From peer: 6.6.6.6
Route: Winner
Origin: IGP
AS Path: 6 {9 10}
Nexthop: 4004::1
Multiple Exit Discriminator: 0
Local Preference: 100
Aggregator: 6.6.6.6
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