OSPF IPv6 - Summarization
Summarization
OSPF (Open Shortest Path First) for IPv6 summarization is a technique employed to streamline routing information within an OSPF Autonomous System (AS). IPv6 summarization involves consolidating multiple individual prefixes into a more concise summary route, reducing the size and complexity of the OSPF routing tables. This process is typically carried out at the Area Border Router (ABR) or Autonomous System Border Router (ASBR) where external routes or inter-area routes are aggregated into a single, summarizing route advertisement. By presenting a summarized view of the topology, OSPF IPv6 summarization helps minimize the amount of Link State Advertisements (LSAs) exchanged throughout the network, leading to improved scalability and more efficient routing operations. Careful consideration must be given during summarization to ensure that the aggregated prefixes accurately represent the subnets while avoiding unnecessary aggregation that could impact routing accuracy. Proper OSPF IPv6 summarization contributes to a more manageable and optimized routing infrastructure.
Lab:
Disclaimer
This Configuration Guide is designed to assist members to enhance their skills in particular technology area. While every effort has been made to ensure that all material is as complete and accurate as possible, the enclosed material is presented on an Dzas isdz basis. Neither the authors nor Forum assume any liability or responsibility to any person or entity with respect to loss or damages incurred from the information contained in this guide. This configuration guide was developed by Forum. Any similarities between material presented in this configuration guide and any other material is completely coincidental.
Cisco IOS Software, Linux Software (I86BI_LINUX-ADVENTERPRISEK9-M), Version 15.2(4)M1, DEVELOPMENT TEST SOFTWARE
Task 1: Configure IPv6 OSPF Summarization
Step 1: In the configuration mode of router configure 4 loopbacks with network address in sequence
R1:
interface loop0
ipv6 address 11:0:0::1/64
exit
interface loop1
ipv6 address 11:0:1::1/64
exit
interface loop2
ipv6 address 11:0:2::1/64
exit
interface loop3
ipv6 address 11:0:3::1/64
exit
Step 2: Verify routes on neighbor router routing table
R2#show ip route
IPv6 Routing Table - default - 21 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP
O 11:0:1::1/128 [110/64]
via FE80::A8BB:CCFF:FE00:100, Serial2/0
O 11:0:2::1/128 [110/64]
via FE80::A8BB:CCFF:FE00:100, Serial2/0
O 11:0:3::1/128 [110/64]
via FE80::A8BB:CCFF:FE00:100, Serial2/0
C 12::/64 [0/0]
via Serial2/0, directly connected
L 12::A8BB:CCFF:FE00:200/128 [0/0]
via Serial2/0, receive
C 22:0:1::/64 [0/0]
via Loopback1, directly connected
L 22:0:1::2/128 [0/0]
via Loopback1, receive
C 22:0:2::/64 [0/0]
via Loopback1, receive
C 22:0:2::/64 [0/0]
via Loopback2, directly connected
L 22:0:2::2/128 [0/0]
via Loopback2, receive
C 22:0:3::/64 [0/0]
via Loopback3, directly connected
L 22:0:3::2/128 [0/0]
via Loopback3, receive
C 23::/64 [0/0]
via Ethernet0/0, directly connected
L 23::A8BB:CCFF:FE00:200/128 [0/0]
via Ethernet0/0, receive
O 33:0:1::3/128 [110/10]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O 33:0:2::3/128 [110/10]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O 33:0:3::3/128 [110/10]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 34::/64 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 44:0:1::4/128 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 44:0:2::4/128 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 44:0:3::4/128 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
L FF00::/8 [0/0]
via Null0, receive
Step 3: Summarize IPv6 OSPF routes on ABR router
In OSPF Summary is always done on Area Border Router (ABR)
R1:
telnet 12.0.0.2
password: cisco
R2>enable
password: cisco
R2#show ipv6 ospf database
OSPFv3 Router with ID (22.0.3.2) (Process ID 2)
Router Link States (Area 0)
ADV Router Age Seq# Fragment ID Link count Bits
22.0.3.2 1519 0x80000004 0 1 B
33.0.3.3 126 0x80000004 0 1 B
R2(config)#ipv6 router ospf 2
R2(config-rtr)#area 1 range 11::/16
R2(config-rtr)#exit
[Connection to 12.0.0.2 closed by foreign host]
R2:
R2(config)#ipv6 router ospf 2
R2(config-rtr)#area 0 range 22::/16
R2(config-rtr)#exit
telnet 23.0.0.3
password: cisco
R3>enable
password: cisco
R3# show ipv6 ospf database
OSPFv3 Router with ID (33.0.3.3) (Process ID 3)
Router Link States (Area 0)
ADV Router Age Seq# Fragment ID Link count Bits
22.0.3.2 332 0x80000005 0 1 B
33.0.3.3 869 0x80000004 0 1 B
R3(config)#ipv6 router ospf 3
R3(config-rtr)#area 0 range 22::/16
R3(config-rtr)#exit
R3#exit
[Connection to 23.0.0.3 closed by foreign host]
Task 2: Verification:
Step 1: Verify receipt of summary route in neighbor routing table & verify creation of null interface in routing table by following command:
R2#show ip route
IPv6 Routing Table - default - 23 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP
O 11::/16 [110/64]
via Null0, directly connected
O 11:0:1::1/128 [110/64]
via FE80::A8BB:CCFF:FE00:100, Serial2/0
O 11:0:2::1/128 [110/64]
via FE80::A8BB:CCFF:FE00:100, Serial2/0
O 11:0:3::1/128 [110/64]
via FE80::A8BB:CCFF:FE00:100, Serial2/0
C 12::/64 [0/0]
via Serial2/0, directly connected
L 12::A8BB:CCFF:FE00:200/128 [0/0]
via Serial2/0, receive
O 22::/16 [110/0]
via Null0, directly connected
C 22:0:1::/64 [0/0]
via Loopback1, receive
C 22:0:2::/64 [0/0]
via Loopback2, directly connected
L 22:0:2::2/128 [0/0]
via Loopback2, receive
C 22:0:3::/64 [0/0]
via Loopback3, directly connected
L 22:0:3::2/128 [0/0]
via Loopback3, receive
C 23::/64 [0/0]
via Ethernet0/0, directly connected
L 23::A8BB:CCFF:FE00:200/128 [0/0]
via Ethernet0/0, receive
O 33:0:1::3/128 [110/10]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O 33:0:2::3/128 [110/10]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O 33:0:3::3/128 [110/10]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 34::/64 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 44:0:1::4/128 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 44:0:2::4/128 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI 44:0:3::4/128 [110/74]
via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
L FF00::/8 [0/0]
via Null0, receive
ABR Router will send summary routes from one area to other areas. When summarization is configured on a router, same router immediately created a routing point to Null 0 for loop prevention. Hence Null 0 will be created only on ABR routers in OSPF.
R4#show ip route
IPv6 Routing Table - default - 16 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP
OI 11::/16 [110/138]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
OI 12::/64 [110/138]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
OI 22::/16 [110/74]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
OI 23::/64 [110/74]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
OI 33:0:1::3/128 [110/64]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
OI 33:0:2::3/128 [110/64]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
OI 33:0:3::3/128 [110/64]
via FE80::A8BB:CCFF:FE00:300, Serial2/0
C 34::/64 [0/0]
via Serial2/0, directly connected
L 34::A8BB:CCFF:FE00:400/128 [0/0]
via Serial2/0, receive
C 44:0:1::/64 [0/0]
via Loopback1, directly connected
L 44:0:1::4/128 [0/0]
via Loopback1, receive
C 44:0:2::/64 [0/0]
via Loopback2, directly connected
L 44:0:2::4/128 [0/0]
via Loopback2, receive
C 44:0:3::/64 [0/0]
via Loopback3, directly connected
L 44:0:3::4/128 [0/0]
via Loopback3, receive
L FF00::/8 [0/0]
via Null0, receive
Summarized routes is received from inter-area