Summarization on ASBR

OSPF (Open Shortest Path First) for IPv6 summarization on an ASBR (Autonomous System Border Router) involves the aggregation of IPv6 routes to present a more streamlined routing representation at the edge of the OSPF network. The ASBR, acting as a boundary router between OSPF domains and external networks or other OSPF Autonomous Systems, plays a crucial role in summarizing external or inter-area routes into a more compact form for OSPF routers within the domain. This summarization process helps optimize the size of the OSPF routing tables, reducing the number of LSAs (Link State Advertisements) circulated across the network. By aggregating route information, IPv6 summarization on the ASBR enhances network scalability and efficiency. This approach is particularly valuable when connecting OSPF domains to external routing domains, preventing the influx of excessive routing details and contributing to a more efficient and manageable OSPF routing infrastructure. Careful consideration during summarization ensures accuracy in representing subnets, and proper implementation leads to an optimized and well-organized OSPF network.

Lab:

Task 1: Configure IPv6 OSPF Summarization

Step 1: In the configuration mode of router configure 4 loopbacks with network address in sequence

R1:
interface loopback 100
ipv6 address 100:0:0::1/64
exit
interface loopback 101
ipv6 address 100:0:1::1/64
exit
interface loopback 102
ipv6 address 100:0:2::1/64
exit
interface loopback 103
ipv6 address 100:0:3::1/64
exit

Step 2: Redistribute external 100 network on ASBR.

R1:
ipv6 router ospf 1
redistribute connected subnets
exit

Step 3: Verify routes on neighbor router routing table

R2#show ipv6 route
! (Shows router’s routing table and IPv6 entries)

IPv6 Routing Table - default - 26 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
O 12::/61 [110/128]
 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 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
OE2 100::/64 [110/20]
 via FE80::A8BB:CCFF:FE00:100, Serial2/0
OE2 100:0:1::/64 [110/20]
 via FE80::A8BB:CCFF:FE00:100, Serial2/0
OE2 100:0:2::/64 [110/20]
 via FE80::A8BB:CCFF:FE00:100, Serial2/0
OE2 100:0:3::/64 [110/20]
 via FE80::A8BB:CCFF:FE00:100, Serial2/0
L FF00::/8 [0/0]
 via Null0, receive

(E2 means External route type 2, in which will not change cost after every hop throughout the OSPF.)

Step 4: Summarize external routes on ASBR router

! (In external route summary is always done on Autonomous System Border Router (ASBR))

R1:
ipv6 router ospf 1
summary-prefix 100::/16
exit

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:

R1#show ipv6 route

IPv6 Routing Table - default - 30 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
C 11:0:1::/64 [0/0]
 via Loopback1, directly connected
L 11:0:1::1/128 [0/0]
 via Loopback1, receive
C 11:0:2::/64 [0/0]
 via Loopback2, directly connected
L 11:0:2::1/128 [0/0]
 via Loopback2, receive
C 11:0:3::/64 [0/0]
 via Loopback3, directly connected
L 11:0:3::1/128 [0/0]
 via Loopback3, receive
C 12::/61 [0/0]
 via Serial2/0, directly connected
O 12::/64 [110/128]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
L 12::A8BB:CCFF:FE00:100/128 [0/0]
 via Serial2/0, receive
OI 22:0:1::2/128 [110/64]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 22:0:2::2/128 [110/64]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 22:0:3::2/128 [110/64]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 23::/64 [110/74]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 33:0:1::3/128 [110/74]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 33:0:2::3/128 [110/74]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 33:0:3::3/128 [110/74]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 34::/64 [110/138]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 44:0:1::4/128 [110/138]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 44:0:2::4/128 [110/138]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
OI 44:0:3::4/128 [110/138]
 via FE80::A8BB:CCFF:FE00:200, Serial2/0
O 100::/16 [254/20]
 via Null0, directly connected
C 100::/64 [0/0]
 via Loopback100, directly connected
L 100::1/128 [0/0]
 via Loopback100, receive
C 100:0:1::/64 [0/0]
 via Loopback101, directly connected
L 100:0:1::1/128 [0/0]
 via Loopback101, receive
C 100:0:2::/64 [0/0]
 via Loopback102, directly connected
L 100:0:2::1/128 [0/0]
 via Loopback102, receive
C 100:0:3::/64 [0/0]
 via Loopback103, directly connected
L 100:0:3::1/128 [0/0]
 via Loopback103, receive
L FF00::/8 [0/0]
 via Null0, receive

(When summarization is configured on a router; same router immediately created a routing point to Null 0 for loop prevention.)

R2#show ipv6 route
! (Shows router’s routing table and IPv6 routes entries)
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 11:0:1::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
O 12::/61 [110/128]
 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 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
OE2 100::/16 [110/20]
 via FE80::A8BB:CCFF:FE00:100, Serial2/0
L FF00::/8 [0/0]
 via Null0, receive

(Summarized routes are received from external route.)