I would like to know what will happen to a IS-IS broadcast network when the DIS is down or reconnect. I noticed around 20 to 30 seconds of downtime when either 2 of those happen.
I have about 4 routers. Router 1 is the DIS because of the higher priority. When I simulate router 1 being down by turning the interface off, sh ip route isis on the other 3 routers only shows the physical interface connection prefix and but not the passive interfaces.
Continuing from this, sh isis route only shows prefixes attached to the router’s own loopback interface. I see that Router 1 is not showing as a neighbor to the other router as expected with show isis neighbor.
I’m running VyOS 1.4.2
Try the latest rolling, it could be fixed in the T6516
I don’t use advertise-passive-only. Here is the config snippet which is almost identical for all routers:
set protocols isis net 49.0000.0000.0002.0003.00
set protocols isis level level-1
set protocols isis metric-style wide
set protocols isis log-adjacency-changes
set protocols isis set-overload-bit
set protocols isis interface lo passive
set protocols isis interface bond0
set protocols isis interface bond0 priority 1
set protocols isis interface bond0 metric 100000
set protocols isis interface bond0 circuit-type level-1
I only notice the issue if DIS is down or reconnected.
This is the IS-IS summary when I reconnect back Router 1.
Router 1 (the DIS)
$ sh isis summary
vrf : default
Process Id : 1977
System Id : 0000.0002.0001
Up time : 6d18h05m ago
Number of areas : 1
Area VyOS:
Net: 49.0000.0000.0002.0001.00
TX counters per PDU type:
L1 IIH: 202308
L1 LSP: 1476
L1 CSNP: 64035
LSP RXMT: 0
RX counters per PDU type:
L1 IIH: 606594
L1 LSP: 2304
L1 CSNP: 1
L1 PSNP: 22
Drop counters per PDU type:
L1 LSP: 7
Advertise high metrics: Disabled
Level-1:
LSP0 regenerated: 820
LSPs purged: 7
SPF:
minimum interval : 1
IPv4 route computation:
last run elapsed : 00:00:54 ago
last run duration : 415 usec
run count : 3649
IPv6 route computation:
last run elapsed : 00:00:54 ago
last run duration : 177 usec
run count : 3649
Level-2:
LSP0 regenerated: 804
LSPs purged: 0
SPF:
minimum interval : 1
IPv4 route computation:
last run elapsed : 00:02:06 ago
last run duration : 98 usec
run count : 769
IPv6 route computation:
last run elapsed : 00:02:06 ago
last run duration : 86 usec
run count : 769
One of the other routers
$ sh isis summary
vrf : default
Process Id : 1973
System Id : 0000.0002.0003
Up time : 1d05h33m ago
Number of areas : 1
Area VyOS:
Net: 49.0000.0000.0002.0003.00
TX counters per PDU type:
L1 IIH: 37289
L1 LSP: 239
L1 PSNP: 8
LSP RXMT: 0
RX counters per PDU type:
L1 IIH: 109215
L1 LSP: 681
L1 CSNP: 11784
L1 PSNP: 13
Drop counters per PDU type:
L1 LSP: 19
Advertise high metrics: Disabled
Level-1:
LSP0 regenerated: 252
LSPs purged: 3
SPF:
minimum interval : 1
IPv4 route computation:
last run elapsed : 00:02:05 ago
last run duration : 181 usec
run count : 812
IPv6 route computation:
last run elapsed : 00:02:05 ago
last run duration : 110 usec
run count : 812
Ping from one of the other routers to the other. We can see around 25 seconds of downtime and passive prefixes are not showing in show ip route isis.
64 bytes from 10.0.5.33: icmp_seq=37 ttl=64 time=0.282 ms
64 bytes from 10.0.5.33: icmp_seq=38 ttl=64 time=0.285 ms
64 bytes from 10.0.5.33: icmp_seq=39 ttl=64 time=0.222 ms
64 bytes from 10.0.5.33: icmp_seq=40 ttl=64 time=0.224 ms
64 bytes from 10.0.5.33: icmp_seq=41 ttl=64 time=0.283 ms
64 bytes from 10.0.5.33: icmp_seq=42 ttl=64 time=0.285 ms
64 bytes from 10.0.5.33: icmp_seq=43 ttl=64 time=0.286 ms
64 bytes from 10.0.5.33: icmp_seq=44 ttl=64 time=0.286 ms
64 bytes from 10.0.5.33: icmp_seq=69 ttl=64 time=0.155 ms
64 bytes from 10.0.5.33: icmp_seq=70 ttl=64 time=0.117 ms
64 bytes from 10.0.5.33: icmp_seq=71 ttl=64 time=0.138 ms
64 bytes from 10.0.5.33: icmp_seq=72 ttl=64 time=0.212 ms
64 bytes from 10.0.5.33: icmp_seq=73 ttl=64 time=0.246 ms
64 bytes from 10.0.5.33: icmp_seq=74 ttl=64 time=0.203 ms
We’re running VyOS 1.4.2 LTS currently.