Re: ISIS metric delay

Landry Hermann SAMBA · ‎04-17-2022

Hello

I want to configure ISIS protocol with metric based on delay or bandwidth+delay.

I read a document which is not cisco official, below is the point that I saw:

IS-IS uses an arbitrary cost for its metric. IS-IS additionally has three
optional metrics: delay, expense, and error. Cisco does not support
these optional metrics

Does someone can point me to the right cisco reference documentation which can confirm or not Cisco does not support delay, expense and error as metric for ISIS ?

Thank you in advance for your reply

Flavio Miranda · ‎04-17-2022

Hi

On this Book "implementing cisco ip routing (route) foundation learning guide" Cisco mention those metrics. But, this is old stuff and maybe they are not supporting anymore, but they did.

https://books.google.com.br/books?id=f5KssgEfd1IC&pg=PA44&lpg=PA44&dq=isis+metric+metric+%5Bdelay-metric+%5Bexpense&source=bl&ots=8PmOdNFJbA&sig=ACfU3U2_zfJhlHBeSIHncwHV231XNoUo2g&hl=en&sa=X&ved=2ahUKEwiF7r7Gopz3AhUmr5UCHe9MBNAQ6AF6BAgmEAM#v=onepage&...

Georg Pauwen · ‎04-17-2022

Hello,

here is another link to a Cisco Live presentation (slide/page 79) where this is mentioned...

https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2019/pdf/BRKRST-2315.pdf

Landry Hermann SAMBA · ‎05-03-2022

Hello all

Thank you to @Georg Pauwen and @Flavio Miranda for their reply and sharing.

I want to provide more information about what I'm trying to acheave.

My goal is ISIS use also delay to make routing decision.

Find attach all files configuration and my lab network.

Into my lab, I have 2 Cisco ASR 920 (IOS XE 17.6.3) and 1 NCS 540 (IOS XR 7.4.1), MPLS, LDP, ISIS are running fine.

I deliver E-LINE service between lab01-2-cpe and lab01-3-cpe working fine.

I used feature performance-measurement (TWAMP) in order to push delay parameter over the link (lab01-2-asr920 <---->lab01-3-asr920, lab01-2-asr920 <----> lab01-1-ncs540 and lab01-1-ncs540 <------> lab01-3-asr920)

See below ISIS database when performance-measurement (TWAMP) is not active and when it is active.

ISIS database when TWAMP is not active (there is no delay information)

ISIS database when TWAMP is active (there is delay information)

RP/0/RP0/CPU0:lab01-1-ncs540#sh isis database verbose
Tue May 3 09:57:05.786 CEST

IS-IS CORE (Level-2) Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
lab01-2-asr920.00-00 0x00000203 0x628c 1185 /1200 0/0/0
Area Address: 49.0001
NLPID: 0xcc
Hostname: lab01-2-asr920
Metric: 40 IS-Extended lab01-3-asr920.00
Metric: 20 IS-Extended lab01-1-ncs540.00
IP Address: 10.10.10.2
Metric: 0 IP-Extended 10.10.10.2/32
Prefix Attribute Flags: X:0 R:0 N:1 E:0 A:0
Metric: 0 IP-Extended 172.16.2.0/24
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.6/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 40 IP-Extended 192.168.255.2/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
lab01-3-asr920.00-00 0x00000201 0xdc0e 1193 /1200 0/0/0
Area Address: 49.0001
NLPID: 0xcc
Hostname: lab01-3-asr920
Metric: 40 IS-Extended lab01-2-asr920.00
Metric: 20 IS-Extended lab01-1-ncs540.00
IP Address: 10.10.10.3
Metric: 0 IP-Extended 10.10.10.3/32
Prefix Attribute Flags: X:0 R:0 N:1 E:0 A:0
Metric: 0 IP-Extended 172.16.3.0/24
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.8/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 40 IP-Extended 192.168.255.2/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
lab01-1-ncs540.00-00* 0x00000287 0x9970 1089 /* 0/0/0
Area Address: 49.0001
NLPID: 0xcc
IP Address: 10.10.10.4
Metric: 0 IP-Extended 10.10.10.0/24
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.6/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.8/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Hostname: lab01-1-ncs540
Metric: 20 IS-Extended lab01-3-asr920.00
Physical BW: 10000000 kbits/sec
Metric: 20 IS-Extended lab01-2-asr920.00
Physical BW: 10000000 kbits/sec

Total Level-2 LSP count: 3 Local Level-2 LSP count: 1

RP/0/RP0/CPU0:lab01-1-ncs540#sh isis database verbose
Mon May 2 15:11:28.170 CEST

IS-IS CORE (Level-2) Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
lab01-2-asr920.00-00 0x000001ac 0xaf13 883 /1199 0/0/0
Area Address: 49.0001
NLPID: 0xcc
Hostname: lab01-2-asr920
Metric: 20 IS-Extended lab01-1-ncs540.00
Link Average Delay: 103 us
Link Min/Max Delay: 90/127 us
Link Delay Variation: 11 us
Metric: 40 IS-Extended lab01-3-asr920.00
Link Average Delay: 49695 us
Link Min/Max Delay: 195/1769752 us
Link Delay Variation: 76524 us
IP Address: 10.10.10.2
Metric: 0 IP-Extended 10.10.10.2/32
Prefix Attribute Flags: X:0 R:0 N:1 E:0 A:0
Metric: 0 IP-Extended 172.16.2.0/24
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.6/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 40 IP-Extended 192.168.255.2/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
lab01-3-asr920.00-00 0x000001ab 0xbe0c 594 /1199 0/0/0
Area Address: 49.0001
NLPID: 0xcc
Hostname: lab01-3-asr920
Metric: 20 IS-Extended lab01-1-ncs540.00
Link Average Delay: 110 us
Link Min/Max Delay: 93/368 us
Link Delay Variation: 17 us
Metric: 40 IS-Extended lab01-2-asr920.00
Link Average Delay: 25668 us
Link Min/Max Delay: 184/1124201 us
Link Delay Variation: 42553 us
IP Address: 10.10.10.3
Metric: 0 IP-Extended 10.10.10.3/32
Prefix Attribute Flags: X:0 R:0 N:1 E:0 A:0
Metric: 0 IP-Extended 172.16.3.0/24
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.8/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 40 IP-Extended 192.168.255.2/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
lab01-1-ncs540.00-00* 0x00000230 0x8232 1167 /* 0/0/0
Area Address: 49.0001
NLPID: 0xcc
IP Address: 10.10.10.4
Metric: 0 IP-Extended 10.10.10.0/24
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.6/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Metric: 20 IP-Extended 192.168.255.8/31
Prefix Attribute Flags: X:0 R:0 N:0 E:0 A:0
Hostname: lab01-1-ncs540
Metric: 20 IS-Extended lab01-2-asr920.00
Local Interface ID: 42, Remote Interface ID: 25
Interface IP Address: 192.168.255.6
Neighbor IP Address: 192.168.255.7
Physical BW: 10000000 kbits/sec
Link Average Delay: 129 us
Link Min/Max Delay: 102/354 us
Link Delay Variation: 25 us
Metric: 20 IS-Extended lab01-3-asr920.00
Local Interface ID: 41, Remote Interface ID: 25
Interface IP Address: 192.168.255.8
Neighbor IP Address: 192.168.255.9
Physical BW: 10000000 kbits/sec
Link Average Delay: 115 us
Link Min/Max Delay: 100/308 us
Link Delay Variation: 16 us

Total Level-2 LSP count: 3 Local Level-2 LSP count: 1

Question: Does in this case delay information are compute with default metric to best route ?

If you see deeply the ISIS database when TWAMP is active, delay to go from lab01-2-asr920 (loopback 10.10.10.2) to lab01-3-asr920 (loopback 10.10.10.3) is higher than going through lab01-1-ncs540, I expected in terms of routes lab01-2-asr920 in order to go to lab01-3-asr920 choose --> lab01-1-ncs540 then lab01-3-asr920, but it is not working like that, ISIS is still using only default metric then in this case, I have to routes from lab01-2-asr920 to reach lab01-3-asr920 (loopback 0)

lab01-2-asr920#sh ip route 10.10.10.3
Routing entry for 10.10.10.3/32
Known via "isis", distance 115, metric 40, type level-2
Redistributing via isis CORE
Last update from 192.168.255.3 on TenGigabitEthernet0/0/26, 21:03:22 ago
Routing Descriptor Blocks:
* 192.168.255.6, from 10.10.10.3, 21:03:22 ago, via TenGigabitEthernet0/0/24
Route metric is 40, traffic share count is 1
192.168.255.3, from 10.10.10.3, 21:03:22 ago, via TenGigabitEthernet0/0/26
Route metric is 40, traffic share count is 1

lab01-2-asr920#sh ip cef 10.10.10.3
10.10.10.3/32
nexthop 192.168.255.3 TenGigabitEthernet0/0/26
nexthop 192.168.255.6 TenGigabitEthernet0/0/24 label 24000-(local:22)
lab01-2-asr920#

What I can do in order ISIS take into account delay information already present in his database for routing decision ?

Any suggestion will be wellcome

Thank you.