Configure the IPv6 BGP Route Selection Priority

Network Requirements

• Set up IBGP neighbors between Device1 and Device2 and between Device1 and Device3, and set up EBGP neighbors between Device4 and Device2 and between Device4 and Device3.
• Device1 advertises two routes 2001:1::/64 and 2001:2::/64 to Device4, and Device4 advertises two routes 2001:7::/64 and 2001:8::/64 to Device1.
• Modify the Local-preference property of routes on Device2 and Device3 so that Device1 selects route 2001:7::/64 advertised by Device2 and route 2001:8::/64 advertised by Device3 with priority.
• Modify the MED property of routes on Device2 and Device3 so that Device4 selects route 2001:1::/64 advertised by Device3 and route 2001:2::/64 advertised by Device2 with priority.

Network Topology

Figure 13–6 Networking for configuring the IPv6 BGP route selection priority

Configuration Steps

Step 1: Configure the IPv6 global unicast addresses of the interfaces. (Omitted)

Step 2: Configure OSPFv3 so that loopback routes are reachable between devices.

#Configure Device1.

#Configure Device2.

#Configure Device3.

#View the route table of Device1.

Device1#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 1w5d:04:03:11, lo0
LC 1::1/128 [0/0] 
     via ::, 00:08:39, loopback0
O 2::2/128 [110/2] 
     via fe80::201:7aff:fe5e:87da, 00:02:04, vlan2
O  3::3/128 [110/2] 
     via fe80::201:7aff:fec0:525b, 00:00:38, vlan3
C  2001:1::/64 [0/0] 
     via ::, 00:09:12, gigabitethernet0/2/3
L 2001:1::1/128 [0/0] 
     via ::, 00:09:11, lo0 
C 2001:2::/64 [0/0] 
     via ::, 00:08:26, gigabitethernet0/2/2
L 2001:2::1/128 [0/0] 
     via ::, 00:08:26, gigabitethernet0/2/2
C 2001:3::/64 [0/0] 
     via ::, 00:09:01, vlan2
L 2001:3::1/128 [0/0] 
     via ::, 00:09:00, lo0
C 2001:4::/64 [0/0] 
     via ::, 00:08:55, vlan3
L 2001:4::1/128 [0/0] 
     via ::, 00:08:53, lo0 

#View the route table of Device2.

Device2#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 2w4d:23:16:51, lo0
O 1::1/128 [110/2] 
     via fe80::201:7aff:fe62:bb7f, 00:04:25, vlan2
LC 2::2/128 [0/0] 
     via ::, 00:09:31, loopback0
O 3::3/128 [110/3] 
     via fe80::201:7aff:fe62:bb7f, 00:02:52, vlan2
C  2001:3::/64 [0/0] 
     via ::, 00:09:49, vlan2
L 2001:3::2/128 [0/0] 
     via ::, 00:09:48, lo0
O 2001:4::/64 [110/2] 
     via fe80::201:7aff:fe62:bb7f, 00:04:25, vlan2
C  2001:5::/64 [0/0] 
     via ::, 00:09:39, vlan3
L 2001:5::2/128 [0/0] 
     via ::, 00:09:38, lo0 

#View the route table of Device3.

Device3#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 2w1d:22:16:55, lo0
O 1::1/128 [110/2] 
     via fe80::201:7aff:fe62:bb80, 00:04:27, vlan2
O  2::2/128 [110/3] 
     via fe80::201:7aff:fe62:bb80, 00:04:27, vlan2
LC 3::3/128 [0/0] 
     via ::, 00:10:48, loopback0
O 2001:3::/64 [110/2] 
     via fe80::201:7aff:fe62:bb80, 00:04:27, vlan2
C  2001:4::/64 [0/0] 
     via ::, 00:11:55, vlan2
L 2001:4::2/128 [0/0] 
     via ::, 00:11:54, lo0
C 2001:6::/64 [0/0] 
     via ::, 00:11:48, vlan3
L 2001:6::2/128 [0/0] 
     via ::, 00:11:47, lo0 

According to the route table, Device1, Device2, and Device3 have learnt the routes of the loopback interfaces of each other.

Step 3: Configure the IPv6 BGP basic functions.

#Configure Device1.

#Configure Device2.

#Configure Device3.

#Configure Device4.

#On Device1, check the IPv6 BGP neighbor status.

Device1#show bgp ipv6 unicast summary  
BGP router identifier 1.1.1.1, local AS number 100
BGP table version is 4 
2 BGP AS-PATH entries
0 BGP community entries 
 
Neighbor    V AS     MsgRcvd MsgSent   TblVer InQ OutQ Up/Down  State/PfxRcd
2::2           4 100   9            10            4        0     0      00:06:18       2 
3::3           4 100   7             8             4        0     0      00:04:29       2 
 
Total number of neighbors 2 

#On Device4, check the IPv6 BGP neighbor status.

Device4#show bgp ipv6 unicast summary  
BGP router identifier 4.4.4.4, local AS number 200
BGP table version is 4 
2 BGP AS-PATH entries
0 BGP community entries 
 
Neighbor    V  AS    MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2001:5::2   4 100   6            5           4        0     0      00:02:43       2 
2001:6::2   4 100   5            6           4        0     0      00:02:32       2 
 
Total number of neighbors 2

IBGP neighbors have been set up between Device1 and Device2 and between Device2 and Device3, and EBGP neighbors have been set up between Device4 and Device2 and between Device4 and Device3.

#View the route table of Device1.

Device1#show bgp ipv6 unicast  
BGP table version is 4, local router ID is 1.1.1.1 
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              S Stale 
Origin codes: i - IGP, e - EGP, ? - incomplete 

           Network          Next Hop    Metric  LocPrf Weight  Path
[B]*> 2001:1::/64         ::           0                   32768   i
[B]*> 2001:2::/64         ::           0                   32768   i
[B]* i 2001:7::/64        3::3         0         100     0          200 i
[B]*>i                         2::2          0         100     0          200 i
[B]*>i2001:8::/64       2::2          0         100     0          200 i
[B]* i                          3::3          0         100     0          200 i 
 
Device1#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 1w5d:04:20:19, lo0 
LC 1::1/128 [0/0] 
     via ::, 00:25:47, loopback0
O 2::2/128 [110/2] 
     via fe80::201:7aff:fe5e:87da, 00:19:12, vlan2
O  3::3/128 [110/2] 
     via fe80::201:7aff:fec0:525b, 00:17:46, vlan3
C  2001:1::/64 [0/0] 
     via ::, 00:26:20, gigabitethernet0/2/3
L 2001:1::1/128 [0/0] 
     via ::, 00:26:19, lo0
C 2001:2::/64 [0/0] 
     via ::, 00:25:34, gigabitethernet0/2/2
L 2001:2::1/128 [0/0] 
     via ::, 00:25:34, gigabitethernet0/2/2
C 2001:3::/64 [0/0] 
     via ::, 00:26:09, vlan2
L 2001:3::1/128 [0/0] 
     via ::, 00:26:08, lo0
C 2001:4::/64 [0/0] 
     via ::, 00:26:03, vlan3
L 2001:4::1/128 [0/0] 
     via ::, 00:26:01, lo0
B 2001:7::/64 [200/0] 
     via 2::2, 00:03:21, vlan2
B 2001:8::/64 [200/0] 
     via 2::2, 00:02:57, vlan2 

According to the route table, both route 2001:7::/64 and route 2001:8::/64 of Device1 select Device2 as the next-hop device.

#Query the route table of Device4.

Device4#show bgp ipv6 unicast  
BGP table version is 4, local router ID is 4.4.4.4 
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              S Stale 
Origin codes: i - IGP, e - EGP, ? - incomplete 

         Network                Next Hop           Metric  LocPrf Weight Path
[B]*   2001:1::/64         2001:6::2           0                  0         100 i
[B]*>                            2001:5::2           0                 0         100 i
[B]*   2001:2::/64         2001:6::2           0                  0         100 i
[B]*>                           2001:5::2            0                 0         100 i
[B]*> 2001:7::/64        ::                        0                 32768   i 
[B]*> 2001:8::/64        ::                        0                 32768   i 
 
Device4#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 1w5d:04:14:15, lo0
B 2001:1::/64 [20/0] 
     via 2001:5::2, 00:06:52, vlan2
B 2001:2::/64 [20/0] 
     via 2001:5::2, 00:06:52, vlan2
C 2001:5::/64 [0/0] 
     via ::, 00:26:17, vlan2
L 2001:5::1/128 [0/0] 
     via ::, 00:26:16, lo0
C 2001:6::/64 [0/0] 
     via ::, 00:26:24, vlan3
L 2001:6::1/128 [0/0] 
     via ::, 00:26:23, lo0
C 2001:7::/64 [0/0] 
     via ::, 00:25:53, gigabitethernet0/2/3
L 2001:7::1/128 [0/0] 
     via ::, 00:25:51, lo0
C 2001:8::/64 [0/0] 
     via ::, 00:25:40, gigabitethernet0/2/2
L 2001:8::1/128 [0/0] 
     via ::, 00:25:40, gigabitethernet0/2/2 

Both route 2001:1::/64 and 2001:2::/64 of Device4 select Device3 as the next-hop device.

Step 4: Configure an ACL and routing policy to set local-preference and metric.

#Configure Device2.

On Device2, configure a routing policy to set local-preference of route 2001:8::/64 to 110, and set metric of route 2001:1::/64 to 100.

#Configure Device3.

On Device3, configure a routing policy to set local-preference of route 2001:7::/64 to 110, and set metric of route 2001:2::/64 to 100.

• ---

  In configuring a routing policy, you can create a filtration rule based on a prefix list or ACL. The prefix list can precisely match routing masks while the ACL cannot match routing masks.

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Step 5: Configure a routing policy for IPv6 BGP.

#Configure Device2.

On Device2, configure the outgoing direction of neighbor 1::1 to modify local-preference of route 2001:8::/64, and configure the outgoing direction of neighbor 2001:5::1 to modify metric of route 2001:1::/64.

#Configure Device3.

On Device3, configure the outgoing direction of neighbor 10.0.0.1 to modify local-preference of route 2001:7::/64, and configure the outgoing direction of neighbor 2001:6::1 to modify metric of route2001:2::/64.

After a routing policy is configured on the neighbor, you need to reset the neighbor.

Step 6: Check the result.

#View the route table of Device1.

Device1#show bgp ipv6 unicast  
BGP table version is 9, local router ID is 1.1.1.1 
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              S Stale 
Origin codes: i - IGP, e - EGP, ? - incomplete 

           Network          Next Hop      Metric  LocPrf Weight Path
[B]*>  2001:1::/64         ::            0                   32768  i
[B]*>  2001:2::/64         ::            0                   32768  i
[B]* i   2001:7::/64        2::2         0         100     0         200 i
[B]*>i                            3::3         0         110     0        200 i
[B]*>i 2001:8::/64         2::2         0         110     0        200 i
[B]* i                             3::3         0         100     0        200 i 
 
Device1#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 1w5d:04:59:59, lo0
LC 1::1/128 [0/0] 
     via ::, 01:05:27, loopback0
O 2::2/128 [110/2] 
     via fe80::201:7aff:fe5e:87da, 00:58:52, vlan3
O  3::3/128 [110/2] 
     via fe80::201:7aff:fec0:525b, 00:57:26, gigabitethernet0/2/2
C  2001:1::/64 [0/0] 
     via ::, 01:06:00, vlan2
L 2001:1::1/128 [0/0] 
     via ::, 01:05:59, lo0
C 2001:2::/64 [0/0] 
     via ::, 01:05:14, loopback1
L 2001:2::1/128 [0/0] 
     via ::, 01:05:14, loopback1
C 2001:3::/64 [0/0] 
     via ::, 01:05:49, vlan3
L 2001:3::1/128 [0/0] 
     via ::, 01:05:48, lo0 
C 2001:4::/64 [0/0] 
     via ::, 01:05:43, gigabitethernet0/2/2
L 2001:4::1/128 [0/0] 
     via ::, 01:05:41, lo0
B 2001:7::/64 [200/0] 
     via 3::3, 00:09:05, vlan3
B 2001:8::/64 [200/0] 
     via 2::2, 00:04:58, vlan2 

According to the route table, local-preference of routes 2001:7::/64 and 2001:8::/64 is modified successfully, and Device1 select route 2001:8::/64 that is advertised by Device2 and route2001:7::/64 that is advertised by Device3 with priority.

#Query the route table of Device4.

Device4#show bgp ipv6 unicast  
BGP table version is 5, local router ID is 4.4.4.4 
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              S Stale 
Origin codes: i - IGP, e - EGP, ? - incomplete 

           Network           Next Hop         Metric  LocPrf    Weight  Path
[B]*    2001:1::/64      2001:5::2                  100        0         100 i
[B]*>                         2001:6::2        0                      0         100 i
[B]*>  2001:2::/64     2001:5::2        0                      0          100 i
[B]*                           2001:6::2                   100        0         100 i
[B]*> 2001:7::/64         ::                 0                      32768   i
[B]*> 2001:8::/64         ::                 0                      32768   i 
  
Device4#show ipv6 route 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management 
 
L ::1/128 [0/0] 
     via ::, 1w5d:04:53:45, lo0
B 2001:1::/64 [20/0] 
     via 2001:6::2, 00:12:10, vlan3
B 2001:2::/64 [20/0] 
     via 2001:5::2, 00:07:40, vlan2
C 2001:5::/64 [0/0] 
     via ::, 01:05:47, vlan2
L 2001:5::1/128 [0/0] 
     via ::, 01:05:46, lo0
C 2001:6::/64 [0/0] 
     via ::, 01:05:54, vlan3
L 2001:6::1/128 [0/0] 
     via ::, 01:05:52, lo0
C 2001:7::/64 [0/0] 
     via ::, 01:05:22, gigabitethernet0/2/3
L 2001:7::1/128 [0/0] 
     via ::, 01:05:21, lo0
C 2001:8::/64 [0/0] 
     via ::, 01:05:09, gigabitethernet0/2/2
L 2001:8::1/128 [0/0] 
     via ::, 01:05:09, gigabitethernet0/2/2 

According to the route table, metric of routes 2001:1::/64 and 2001:2::/64 is modified successfully, and Device4 select route 2001:2::/64 that is advertised by Device2 and route 2001:1::/64 that is advertised by Device3 with priority.

• ---

  A routing policy can be used in the outgoing direction of route advertisement, and it can also be used in the incoming direction of route receiving.

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