This is a brief article which displays the contents of the LSPDB when using IPv4 and IPv6.
First we will configure IPv4 only. This is a simple L1 only, single area topology.
#R1
hostname R1
line con 0
logging sync
!
router isis
net 49.0001.0000.0000.0001.00
is-type level-1
!
int gi1
ip address 222.222.10.1 255.255.255.0
ip router isis
no shut
#R2
hostname R2
line con 0
logging sync
!
router isis
net 49.0001.0000.0000.0002.00
is-type level-1
!
int gi1
ip address 222.222.10.2 255.255.255.0
ip router isis
no shut
!
int gi2
ip address 222.222.30.2 255.255.255.0
ip router isis
isis network point-to-point
no shut
!
int gi3
ip address 222.222.20.2 255.255.255.0
ip router isis
no shut
#R3
hostname R3
line con 0
logging sync
!
router isis
net 49.0001.0000.0000.0003.00
is-type level-1
!
int gi1
ip address 222.222.30.3 255.255.255.0
ip router isis
isis network point-to-point
no shut
R1#show isis data detail
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
R1.00-00 * 0x000002E2 0xBC5F 1113/* 0/0/0
Area Address: 49.0001
NLPID: 0xCC
Hostname: R1
Metric: 10 IS R2.01
IP Address: 222.222.10.1
Metric: 10 IP 222.222.10.0 255.255.255.0
R2.00-00 0x0000000A 0x8E66 1139/1199 0/0/0
Area Address: 49.0001
NLPID: 0xCC
Hostname: R2
Metric: 10 IS R2.01
Metric: 10 IS R3.00
IP Address: 222.222.20.2
Metric: 10 IP 222.222.10.0 255.255.255.0
Metric: 10 IP 222.222.30.0 255.255.255.0
Metric: 10 IP 222.222.20.0 255.255.255.0
R2.01-00 0x00000001 0x7CD6 987/1199 0/0/0
Metric: 0 IS R2.00
Metric: 0 IS R1.00
R3.00-00 0x00000004 0xAA25 1139/1199 0/0/0
Area Address: 49.0001
NLPID: 0xCC
Hostname: R3
Metric: 10 IS R2.00
IP Address: 222.222.30.3
Metric: 10 IP 222.222.30.0 255.255.255.0
ISIS operates differently than OSPFv2 when it comes to dissementing link-state information. Instead of LSA Types, ISIS uses TLVs. Each TLV is not mentioned in the database output. Instead the total information learned from all TLVs is displayed at once.
The *.01-00 LSPID is only generated by the pseudonode (DIS) for a broadcast domain. This lists the attached routers to the broadcast domain, similar to a Type 2 OSFP LSA.
The *.00-00 LSPIDs are generated by each router. These list attached neighbors and the metric to those neighbors, prefixes attached to the router, IP addresses attached to the router, and the hostname of the router.
Common TLVs
TLV
Information
Example
1
Area address(es)
49.0001
2
IS Reachability (Neighbors)
0000.0000.0002.01
137
Hostname
R1
129
Protocols Supported
IPv4
128
IP Internal reachability (prefixes)
222.222.10.0/24
132
Interface addresses
222.222.10.1
232
IPv6 Interface addresses
2001:a:a:10::1
236
IPv6 reachability (prefixes)
2001:a:a:10::/64
IPv6 configuration
#R1
ipv6 unicast-routing
!
router isis
net 49.0001.0000.0000.0001.00
address-family ipv6
is-type level-1
!
int gi1
no ip address
ipv6 address 2001:a:a:10::1/64
ipv6 router isis
#R2
ipv6 unicast-routing
!
int gi1
no ip address
ipv6 address 2001:a:a:10::2/64
ipv6 router isis
!
int gi2
no ip address
ipv6 address 2001:a:a:30::2/64
ipv6 router isis
isis network point-to-point
!
int gi3
no ip address
ipv6 address 2001:a:a:20::2/64
ipv6 router isis
#R3
ipv6 unicast-routing
!
int gi1
no ip address
ipv6 address 2001:a:a:30::3/64
ipv6 router isis
isis network point-to-point
R1#show isis database detail
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
R1.00-00 * 0x000002E8 0x3190 1029/* 0/0/0
Area Address: 49.0001
NLPID: 0xCC 0x8E
Hostname: R1
Metric: 10 IS R2.01
IPv6 Address: 2001:A:A:10::1
Metric: 10 IPv6 2001:A:A:10::/64
R2.00-00 0x00000014 0xDDCB 1150/1199 0/0/0
Area Address: 49.0001
NLPID: 0xCC 0x8E
Hostname: R2
Metric: 10 IS R2.01
Metric: 10 IS R3.00
IPv6 Address: 2001:A:A:20::2
Metric: 10 IPv6 2001:A:A:10::/64
Metric: 10 IPv6 2001:A:A:30::/64
Metric: 10 IPv6 2001:A:A:20::/64
R2.01-00 0x00000004 0x76D9 1028/1199 0/0/0
Metric: 0 IS R2.00
Metric: 0 IS R1.00
R3.00-00 0x0000000A 0x114C 1150/1199 0/0/0
Area Address: 49.0001
NLPID: 0xCC 0x8E
Hostname: R3
Metric: 10 IS R2.00
IPv6 Address: 2001:A:A:30::3
Metric: 10 IPv6 2001:A:A:30::/64
The only difference between the database now is that there are IPv6 addresses instead of IPv4 addresses, and there is an additional network layer protocol supported, IPv6 (0x8E) compared to just IPv4 (0xCC) before. Notice that both IPv4 and IPv6 are listed as being supported. IOS-XE by default uses single-topology IPv6, which means that both IPv4 and IPv6 use the same underlying network topology at the same time. This allows for optimization, as two separate topologies are kept (one for IPv4 and one for IPv6). For details, see the Multitopology ISIS article. Also notice that wide metrics are not required to use ISIS for IPv6.
