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is-is metricS

IS-IS | Metric, Wide Metrics and Reference-Bandwidth

  • All IS-IS routes have a cost, which is a routing metric that is used in the IS-IS link-state calculation.
  • All IS-IS links use a metric of 10 by default. Normally, IS-IS metrics can have values up to 63. The total cost to a destination is the sum of the metrics on all outgoing interfaces along a particular path from the source to the destination. By default, the total path metric is limited to 1023. Optimize routing based on bandwidth by setting the reference bandwidth used in calculating the default interface cost.

Juniper vMX 14 & EVE-NG Pro is used for this lab.

 Devices Configuration: 

[email protected]> show configuration |display set 
set version 14.1R4.8
set system host-name R1
set system root-authentication encrypted-password "$1$wkhQZFVm$nru6IIXbJwXCecxudADMu."
set system syslog user * any emergency
set system syslog file messages any notice
set system syslog file messages authorization info
set system syslog file interactive-commands interactive-commands any
set interfaces ge-0/0/0 speed 1g
set interfaces ge-0/0/0 unit 0 family inet address 12.12.12.1/24
set interfaces ge-0/0/0 unit 0 family iso
set interfaces ge-0/0/1 speed 10g
set interfaces ge-0/0/1 unit 0 family inet address 13.13.13.1/24
set interfaces ge-0/0/1 unit 0 family iso
set interfaces lo0 unit 1 family inet address 1.1.1.1/32
set interfaces lo0 unit 1 family iso address 49.0001.0010.0100.1001.00
set protocols isis reference-bandwidth 100g
set protocols isis level 1 wide-metrics-only
set protocols isis level 2 wide-metrics-only
set protocols isis interface ge-0/0/0.0
set protocols isis interface ge-0/0/1.0
set protocols isis interface lo0.1    
[email protected]> show configuration |display set 
set version 14.1R4.8
set system host-name R2
set system root-authentication encrypted-password "$1$spmjNjUO$wP.uxAc4I/QzeoHow.Vmw0"
set system syslog user * any emergency
set system syslog file messages any notice
set system syslog file messages authorization info
set system syslog file interactive-commands interactive-commands any
set interfaces ge-0/0/0 speed 1g
set interfaces ge-0/0/0 unit 0 family inet address 12.12.12.2/24
set interfaces ge-0/0/0 unit 0 family iso
set interfaces ge-0/0/1 speed 1g
set interfaces ge-0/0/1 unit 0 family inet address 24.24.24.2/24
set interfaces ge-0/0/1 unit 0 family iso
set interfaces lo0 unit 2 family inet address 2.2.2.2/32
set interfaces lo0 unit 2 family iso address 49.0001.0020.0200.2002.00
set protocols isis reference-bandwidth 100g
set protocols isis level 1 wide-metrics-only
set protocols isis level 2 wide-metrics-only
set protocols isis interface ge-0/0/0.0
set protocols isis interface ge-0/0/1.0
set protocols isis interface lo0.2 
[email protected]> show configuration |display set 
set version 14.1R4.8
set system host-name R3
set system root-authentication encrypted-password "$1$MGYf5.cc$bz7lkovLwOV2dlZ6tkPyP/"
set system syslog user * any emergency
set system syslog file messages any notice
set system syslog file messages authorization info
set system syslog file interactive-commands interactive-commands any
set interfaces ge-0/0/1 speed 100m
set interfaces ge-0/0/1 unit 0 family inet address 13.13.13.3/24
set interfaces ge-0/0/1 unit 0 family iso
set interfaces ge-0/0/2 speed 100m
set interfaces ge-0/0/2 unit 0 family inet address 34.34.34.3/24
set interfaces ge-0/0/2 unit 0 family iso
set interfaces lo0 unit 3 family inet address 3.3.3.3/32
set interfaces lo0 unit 3 family iso address 49.0010.0030.0300.3003.00
set protocols isis reference-bandwidth 10g
set protocols isis level 1 wide-metrics-only
set protocols isis level 2 wide-metrics-only
set protocols isis interface ge-0/0/1.0
set protocols isis interface ge-0/0/2.0
set protocols isis interface lo0.3
[email protected]> show configuration |display set 
set version 14.1R4.8
set system host-name R4
set system root-authentication encrypted-password "$1$kWZlROQ8$G2PzsrKqDiFbLr1uxAwBE0"
set system syslog user * any emergency
set system syslog file messages any notice
set system syslog file messages authorization info
set system syslog file interactive-commands interactive-commands any
set interfaces ge-0/0/1 speed 1g
set interfaces ge-0/0/1 unit 0 family inet address 24.24.24.4/24
set interfaces ge-0/0/1 unit 0 family iso
set interfaces ge-0/0/2 speed 10g
set interfaces ge-0/0/2 unit 0 family inet address 34.34.34.4/24
set interfaces ge-0/0/2 unit 0 family iso
set interfaces lo0 unit 4 family inet address 4.4.4.4/32
set interfaces lo0 unit 4 family iso address 49.0001.0040.0400.4004.00
set protocols isis reference-bandwidth 100g
set protocols isis level 1 wide-metrics-only
set protocols isis level 2 wide-metrics-only
set protocols isis interface ge-0/0/1.0
set protocols isis interface ge-0/0/2.0
set protocols isis interface lo0.4
— Configuration | Verification —

— ISIS Neighbor:

[email protected]> show isis adjacency 
Interface             System         L State        Hold (secs) SNPA
ge-0/0/0.0            R2             1  Up                    6  0:5:86:71:ae:0
ge-0/0/0.0            R2             2  Up                    7  0:5:86:71:ae:0
ge-0/0/1.0            R3             2  Up                    6  0:5:86:71:ae:1

[email protected]> show isis adjacency 
Interface             System         L State        Hold (secs) SNPA
ge-0/0/0.0            R1             1  Up                   25  0:5:86:71:2e:0
ge-0/0/0.0            R1             2  Up                   21  0:5:86:71:2e:0
ge-0/0/1.0            R4             1  Up                   26  0:5:86:71:52:1
ge-0/0/1.0            R4             2  Up                   23  0:5:86:71:52:1

[email protected]> show isis adjacency 
Interface             System         L State        Hold (secs) SNPA
ge-0/0/1.0            R1             2  Up                   21  0:5:86:71:2e:1
ge-0/0/2.0            R4             2  Up                   23  0:5:86:71:52:2

[email protected]> show isis adjacency 
Interface             System         L State        Hold (secs) SNPA
ge-0/0/1.0            R2             1  Up                    7  0:5:86:71:ae:1
ge-0/0/1.0            R2             2  Up                    6  0:5:86:71:ae:1
ge-0/0/2.0            R3             2  Up                    7  0:5:86:71:ae:2

-- Default: R1 use R2 to reach R4, with default metric 10 --
Note: default metric for every isis interface = 10, This may cause; Asymmetric routing.

[email protected]> ping 4.4.4.4 
PING 4.4.4.4 (4.4.4.4): 56 data bytes
64 bytes from 4.4.4.4: icmp_seq=0 ttl=63 time=27.942 ms
64 bytes from 4.4.4.4: icmp_seq=1 ttl=63 time=3.285 ms

[email protected]> traceroute 4.4.4.4 
traceroute to 4.4.4.4 (4.4.4.4), 30 hops max, 40 byte packets
 1  12.12.12.2 (12.12.12.2)  8.098 ms  1.404 ms  1.370 ms
 2  4.4.4.4 (4.4.4.4)  6.056 ms  3.002 ms  2.901 ms
 
[email protected]R1> show isis interface 
IS-IS interface database:
Interface             L CirID Level 1 DR        Level 2 DR        L1/L2 Metric
ge-0/0/0.0            3   0x1 R2.02             R2.02                  10/10
ge-0/0/1.0            3   0x1 R1.00             R3.02                  10/10

[email protected]R4> traceroute 1.1.1.1 
traceroute to 1.1.1.1 (1.1.1.1), 30 hops max, 40 byte packets
 1  24.24.24.2 (24.24.24.2)  3.786 ms  1.575 ms  1.347 ms
 2  1.1.1.1 (1.1.1.1)  6.138 ms  2.335 ms  2.128 ms

 

— Change BW as; R1-R2-R4 = 1G | R1-R3-R4 = 10G

[email protected]# show |compare 
[edit interfaces ge-0/0/0]
+   speed 1g;
[edit interfaces ge-0/0/1]
+   speed 10g;

[email protected]# show |compare 
[edit interfaces ge-0/0/0]
+   speed 1g;
[edit interfaces ge-0/0/1]
+   speed 1g;

[email protected]# show |compare 
[edit interfaces ge-0/0/1]
+   speed 1g;
[edit interfaces ge-0/0/2]
+   speed 1g;

[email protected]# show |compare 
[edit interfaces ge-0/0/1]
+   speed 1g;
[edit interfaces ge-0/0/2]
+   speed 10g;
[email protected]> traceroute 4.4.4.4 source 1.1.1.1    
traceroute to 4.4.4.4 (4.4.4.4) from 1.1.1.1, 30 hops max, 40 byte packets
 1  12.12.12.2 (12.12.12.2)  3.194 ms  1.273 ms  1.586 ms
 2  4.4.4.4 (4.4.4.4)  2.430 ms  2.007 ms  2.960 ms
--- Still same path from R1 to R4?
    Because: Lower metric WIN's, plus Changing interface BW, will not work and path will not change....
    Need to use reference BW as well.
                        
On all four Routers;
# set protocols isis reference-bandwidth 100g
This will change metric as;
R1--R3---R4 = 100/100
R1--R2--R4 = 10/10

[email protected]> show isis interface IS-IS interface database: Interface L CirID Level 1 DR Level 2 DR L1/L2 Metric ge-0/0/0.0 3 0x1 R2.02 R2.02 100/100 ge-0/0/1.0 3 0x1 R1.00 R1.00 10/10 [email protected]> show isis interface IS-IS interface database: Interface L CirID Level 1 DR Level 2 DR L1/L2 Metric ge-0/0/0.0 3 0x2 R2.02 R2.02 100/100 ge-0/0/1.0 3 0x3 R2.00 R2.00 100/100 [email protected]> show isis interface IS-IS interface database: Interface L CirID Level 1 DR Level 2 DR L1/L2 Metric ge-0/0/1.0 3 0x2 R3.00 R3.00 10/10 ge-0/0/2.0 3 0x3 R3.00 R3.03 10/10 [email protected]> show isis interface IS-IS interface database: Interface L CirID Level 1 DR Level 2 DR L1/L2 Metric ge-0/0/1.0 3 0x1 R4.00 R4.00 100/100 ge-0/0/2.0 3 0x1 R4.00 R3.03 10/10 [email protected]> show route protocol isis inet.0: 10 destinations, 10 routes (10 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 2.2.2.2/32 *[IS-IS/15] 00:07:27, metric 63 > to 12.12.12.2 via ge-0/0/0.0 3.3.3.3/32 *[IS-IS/18] 00:14:18, metric 10 > to 13.13.13.3 via ge-0/0/1.0 4.4.4.4/32 *[IS-IS/15] 00:07:27, metric 73 > to 12.12.12.2 via ge-0/0/0.0 24.24.24.0/24 *[IS-IS/15] 00:07:27, metric 73 > to 12.12.12.2 via ge-0/0/0.0 34.34.34.0/24 *[IS-IS/15] 00:07:27, metric 83 > to 12.12.12.2 via ge-0/0/0.0 Note that metric is either 63, 73, or 83 however we should see metric as 10, 100 after changing metric/ref-bw. To fix or to display correct metric, use isis wide-metric command.

— Correct Metric us ‘wide-metric’ command on all routers:

Applied under specific ISIS levels (level1/level2). LOWER METRIC IS PREFER'D (same like OSPF)

set protocols isis level 1 wide-metrics-only set protocols isis level 2 wide-metrics-only
 
[email protected]> show route protocol isis 

inet.0: 10 destinations, 10 routes (10 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

2.2.2.2/32         *[IS-IS/15] 00:02:12, metric 100
                    > to 12.12.12.2 via ge-0/0/0.0
3.3.3.3/32         *[IS-IS/18] 00:01:40, metric 10
                    > to 13.13.13.3 via ge-0/0/1.0
4.4.4.4/32         *[IS-IS/15] 00:01:46, metric 200
                    > to 12.12.12.2 via ge-0/0/0.0
24.24.24.0/24      *[IS-IS/15] 00:02:12, metric 200
                    > to 12.12.12.2 via ge-0/0/0.0
34.34.34.0/24      *[IS-IS/15] 00:01:46, metric 210
                    > to 12.12.12.2 via ge-0/0/0.0

iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

-- Correct Metric is displayed now --

— TEST:

[email protected]# show |compare 
[edit interfaces ge-0/0/1]
-   speed 10g;
+   speed 100m;
[edit interfaces ge-0/0/2]
-   speed 10g;
+   speed 100m;

# set protocols isis reference-bandwidth 10g

[email protected]> traceroute 4.4.4.4    
traceroute to 4.4.4.4 (4.4.4.4), 30 hops max, 40 byte packets
 1  13.13.13.3 (13.13.13.3)  3.016 ms  1.484 ms  1.486 ms
 2  4.4.4.4 (4.4.4.4)  2.722 ms  2.967 ms  2.415 ms
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