ISIS on Huawei routers

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ISIS is a link-state IGP protocol. It gathers routing information from adjacent neighbors and uses the SPF algorithm to determine the best paths to destinations.

I wouldn’t like to focus on the theory because you can find it in many sources.

Let’s configure ISIS protocol based on the following topology:

ISIS on Huawei router topology

Configure IP addresses of physical and loopback interfaces on all routers (it is omitted here):

<1> dis ip interface brief 

Interface                         IP Address/Mask      Physical   Protocol  
Ethernet0/0/8                     10.0.0.1/30          up         up        
LoopBack0                         1.1.1.1/32           up         up(s)      

<2> dis ip interface brief 

Interface                         IP Address/Mask      Physical   Protocol  
Ethernet2/0/0                     10.0.0.2/30          up         up           
GigabitEthernet0/0/0              20.0.0.1/30          up         up        
GigabitEthernet0/0/1              10.0.2.2/30          up         up        
LoopBack0                         2.2.2.2/32           up         up(s)     

<3> dis ip interface brief 

Interface                         IP Address/Mask      Physical   Protocol  
GigabitEthernet0/0/0              10.0.2.1/30          up         up        
GigabitEthernet0/0/1              30.0.0.1/30          up         up          
LoopBack0                         3.3.3.3/32           up         up(s)      

<4> dis ip interface br

Interface                         IP Address/Mask      Physical   Protocol  
Ethernet4/0/0                     40.0.0.1/30          up         up            
GigabitEthernet0/0/0              20.0.0.2/30          up         up        
GigabitEthernet0/0/1              30.0.0.2/30          up         up           
LoopBack0                         4.4.4.4/32           up         up(s)        

<5> dis ip interface brief 

Interface                         IP Address/Mask      Physical   Protocol  
Ethernet0/0/8                     40.0.0.2/30          up         up        
LoopBack0                         5.5.5.5/32           up         up(s)

Configure ISIS globally, on loopback and physical interfaces (router 2 as an example):

[2]isis
[2-isis-1]network-entity 10.0020.0200.2002.00

[2]interface LoopBack 0
[2-LoopBack0]isis enable
[2]interface Ethernet2/0/0
[2-Ethernet2/0/0]isis enable
[2]interface GigabitEthernet0/0/0
[2-GigabitEthernet0/0/0]isis enable 
[2]interface GigabitEthernet0/0/1
[2-GigabitEthernet0/0/1]isis enable

It should be noted at this point that routers 1, 2 and 3 are in area 10 and routers 4 and 5 in area 20. Additionally you should remember about hierarchical structure of ISIS. In our case router 1 works as level-1, routers 2 and 3 work as level-1-2 (by default) and routers 4 and 5 as level-2. Level-1 is an equivalent of the stub area in OSPF. Level-1 routers have only a defult route to external destinations.

[1]isis
[1-isis-1]is-level level-1

[2]isis
[2-isis-1]is-level level-1-2

[3]isis
[3-isis-1]is-level level-1-2

[4]isis
[4-isis-1]is-level level-2

[5]isis
[5-isis-1]is-level level-2

Let’s verify this configuration:

[1]display isis lsdb 

                        Database information for ISIS(1)
                        --------------------------------

                          Level-1 Link State Database

LSPID                 Seq Num      Checksum      Holdtime      Length  ATT/P/OL
-------------------------------------------------------------------------------
0010.0100.1001.00-00* 0x0000000d   0x936         667           84      0/0/0   
0020.0200.2002.00-00  0x00000013   0x5d55        705           127     1/0/0   
0020.0200.2002.02-00  0x00000009   0xb1e5        705           55      0/0/0   
0020.0200.2002.03-00  0x00000009   0xd901        705           55      0/0/0   
0030.0300.3003.00-00  0x00000010   0x699b        596           100     1/0/0
0020.0200.2002.02-00
0020.0200.2002 - source ID
02 - pseudonode ID
00 - LSP number

ISIS Level-1 router:

  • has the link state information of the local area
  • finds the nearest level 1-2 router based on ATT bit of the LSP
  • generates a default route through the nearest level-1-2 router to visit the destinations outside this area.
[2]display isis lsdb

                        Database information for ISIS(1)
                        --------------------------------

                          Level-1 Link State Database

LSPID                 Seq Num      Checksum      Holdtime      Length  ATT/P/OL
-------------------------------------------------------------------------------
0010.0100.1001.00-00  0x0000000e   0x737         1030          84      0/0/0   
0020.0200.2002.00-00* 0x00000014   0x5b56        1087          127     1/0/0   
0020.0200.2002.02-00* 0x0000000a   0xafe6        1087          55      0/0/0   
0020.0200.2002.03-00* 0x0000000a   0xd702        1087          55      0/0/0   
0030.0300.3003.00-00  0x00000011   0x679c        931           100     1/0/0   

                          Level-2 Link State Database

LSPID                 Seq Num      Checksum      Holdtime      Length  ATT/P/OL
-------------------------------------------------------------------------------
0020.0200.2002.00-00* 0x00000016   0xdb0         1087          163     0/0/0   
0020.0200.2002.01-00* 0x0000000a   0x1f56        1086          55      0/0/0   
0020.0200.2002.02-00* 0x0000000a   0xafe6        1086          55      0/0/0   
0030.0300.3003.00-00  0x00000014   0x6801        930           159     0/0/0   
0030.0300.3003.02-00  0x0000000a   0xa48b        930           55      0/0/0   
0040.0400.4004.00-00  0x00000010   0x5165        434           138     0/0/0   
0040.0400.4004.03-00  0x00000009   0x9435        434           55      0/0/0   
0050.0500.5005.00-00  0x0000000d   0xaa58        985           84      0/0/0

ISIS Level-1-2 router:

  • forms adjacency with both level-1-2 and level-2 routers
  • contains both level-1 and level-2 LSDBs
  • sets ATT bit in the level-1 LSP originated by itself
  • contains routing information of the whole network.
[4]display isis lsdb

                        Database information for ISIS(1)
                        --------------------------------

                          Level-2 Link State Database

LSPID                 Seq Num      Checksum      Holdtime      Length  ATT/P/OL
-------------------------------------------------------------------------------
0020.0200.2002.00-00  0x00000016   0xdb0         1034          163     0/0/0   
0020.0200.2002.01-00  0x0000000a   0x1f56        1034          55      0/0/0   
0020.0200.2002.02-00  0x0000000a   0xafe6        1034          55      0/0/0   
0030.0300.3003.00-00  0x00000014   0x6801        880           159     0/0/0   
0030.0300.3003.02-00  0x0000000a   0xa48b        880           55      0/0/0   
0040.0400.4004.00-00* 0x00000010   0x5165        385           138     0/0/0   
0040.0400.4004.03-00* 0x00000009   0x9435        385           55      0/0/0   
0050.0500.5005.00-00  0x0000000d   0xaa58        936           84      0/0/0

ISIS Level-2 router:

  • forms adjacency with both level-2 and level-1-2 routers
  • gathers LSPs of all routers in backbone area
  • contains all routing information of the whole routing domain.

Let’s look at ISIS routing tables:

[1]dis isis route 

                         Route information for ISIS(1)
                         -----------------------------

                        ISIS(1) Level-1 Forwarding Table
                        --------------------------------

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
0.0.0.0/0            10         NULL    Eth0/0/8        10.0.0.2        A/-/-/-
10.0.0.0/30          10         NULL    Eth0/0/8        Direct          D/-/L/-
20.0.0.0/30          20         NULL    Eth0/0/8        10.0.0.2        A/-/-/-
30.0.0.0/30          30         NULL    Eth0/0/8        10.0.0.2        A/-/-/-
3.3.3.3/32           20         NULL    Eth0/0/8        10.0.0.2        A/-/-/-
2.2.2.2/32           10         NULL    Eth0/0/8        10.0.0.2        A/-/-/-
10.0.2.0/30          20         NULL    Eth0/0/8        10.0.0.2        A/-/-/-
1.1.1.1/32           0          NULL    Loop0           Direct          D/-/L/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set

A default route must exist in the Level-1 routing table and the next hop is a Level-1-2 router.

[2]dis isis route 

                         Route information for ISIS(1)
                         -----------------------------

                        ISIS(1) Level-1 Forwarding Table
                        --------------------------------

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
0.0.0.0/0            10         NULL   
10.0.0.0/30          10         NULL    Eth2/0/0        Direct          D/-/L/-
20.0.0.0/30          10         NULL    GE0/0/0         Direct          D/-/L/-
30.0.0.0/30          20         NULL    GE0/0/1         10.0.2.1        A/-/L/-
3.3.3.3/32           10         NULL    GE0/0/1         10.0.2.1        A/-/L/-
2.2.2.2/32           0          NULL    Loop0           Direct          D/-/L/-
10.0.2.0/30          10         NULL    GE0/0/1         Direct          D/-/L/-
1.1.1.1/32           10         NULL    Eth2/0/0        10.0.0.1        A/-/L/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set

                        ISIS(1) Level-2 Forwarding Table
                        --------------------------------

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
10.0.0.0/30          10         NULL    Eth2/0/0        Direct          D/-/L/-
20.0.0.0/30          10         NULL    GE0/0/0         Direct          D/-/L/-
30.0.0.0/30          20         NULL   
40.0.0.0/30          20         NULL    GE0/0/0         20.0.0.2        A/-/-/-
3.3.3.3/32           10         NULL   
2.2.2.2/32           0          NULL    Loop0           Direct          D/-/L/-
10.0.2.0/30          10         NULL    GE0/0/1         Direct          D/-/L/-
5.5.5.5/32           20         NULL    GE0/0/0         20.0.0.2        A/-/-/-
1.1.1.1/32           30         NULL   
4.4.4.4/32           10         NULL    GE0/0/0         20.0.0.2        A/-/-/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set

Level-1-2 routers contain both level-1 and level-2 routing tables.

[5]dis isis route

                         Route information for ISIS(1)
                         -----------------------------

                        ISIS(1) Level-2 Forwarding Table
                        --------------------------------

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
10.0.0.0/30          30         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
20.0.0.0/30          20         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
30.0.0.0/30          20         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
40.0.0.0/30          10         NULL    Eth0/0/8        Direct          D/-/L/-
3.3.3.3/32           20         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
2.2.2.2/32           20         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
10.0.2.0/30          30         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
5.5.5.5/32           0          NULL    Loop0           Direct          D/-/L/-
1.1.1.1/32           30         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
4.4.4.4/32           10         NULL    Eth0/0/8        40.0.0.1        A/-/-/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set

A Level-2 router must have all Level-1 and Level-2 routes. We can see it better in IP routing tables:

[1]display ip routing-table 
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 14       Routes : 14       

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        0.0.0.0/0   ISIS-L1 15   10          D   10.0.0.2        Ethernet0/0/8
        1.1.1.1/32  Direct  0    0           D   127.0.0.1       LoopBack0
        2.2.2.2/32  ISIS-L1 15   10          D   10.0.0.2        Ethernet0/0/8
        3.3.3.3/32  ISIS-L1 15   20          D   10.0.0.2        Ethernet0/0/8
       10.0.0.0/30  Direct  0    0           D   10.0.0.1        Ethernet0/0/8
       10.0.0.1/32  Direct  0    0           D   127.0.0.1       Ethernet0/0/8
       10.0.0.3/32  Direct  0    0           D   127.0.0.1       Ethernet0/0/8
       10.0.2.0/30  ISIS-L1 15   20          D   10.0.0.2        Ethernet0/0/8
       20.0.0.0/30  ISIS-L1 15   20          D   10.0.0.2        Ethernet0/0/8
       30.0.0.0/30  ISIS-L1 15   30          D   10.0.0.2        Ethernet0/0/8
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0
127.255.255.255/32  Direct  0    0           D   127.0.0.1       InLoopBack0
255.255.255.255/32  Direct  0    0           D   127.0.0.1       InLoopBack0

[2]dis ip routing-table 
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 20       Routes : 20       

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        1.1.1.1/32  ISIS-L1 15   10          D   10.0.0.1        Ethernet2/0/0
        2.2.2.2/32  Direct  0    0           D   127.0.0.1       LoopBack0
        3.3.3.3/32  ISIS-L1 15   10          D   10.0.2.1        GigabitEthernet0/0/1
        4.4.4.4/32  ISIS-L2 15   10          D   20.0.0.2        GigabitEthernet0/0/0
        5.5.5.5/32  ISIS-L2 15   20          D   20.0.0.2        GigabitEthernet0/0/0
       10.0.0.0/30  Direct  0    0           D   10.0.0.2        Ethernet2/0/0
       10.0.0.2/32  Direct  0    0           D   127.0.0.1       Ethernet2/0/0
       10.0.0.3/32  Direct  0    0           D   127.0.0.1       Ethernet2/0/0
       10.0.2.0/30  Direct  0    0           D   10.0.2.2        GigabitEthernet0/0/1
       10.0.2.2/32  Direct  0    0           D   127.0.0.1       GigabitEthernet0/0/1
       10.0.2.3/32  Direct  0    0           D   127.0.0.1       GigabitEthernet0/0/1
       20.0.0.0/30  Direct  0    0           D   20.0.0.1        GigabitEthernet0/0/0
       20.0.0.1/32  Direct  0    0           D   127.0.0.1       GigabitEthernet0/0/0
       20.0.0.3/32  Direct  0    0           D   127.0.0.1       GigabitEthernet0/0/0
       30.0.0.0/30  ISIS-L1 15   20          D   10.0.2.1        GigabitEthernet0/0/1
       40.0.0.0/30  ISIS-L2 15   20          D   20.0.0.2        GigabitEthernet0/0/0
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0
127.255.255.255/32  Direct  0    0           D   127.0.0.1       InLoopBack0
255.255.255.255/32  Direct  0    0           D   127.0.0.1       InLoopBack0

[5]display ip routing-table 
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 16       Routes : 16       

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        1.1.1.1/32  ISIS-L2 15   30          D   40.0.0.1        Ethernet0/0/8
        2.2.2.2/32  ISIS-L2 15   20          D   40.0.0.1        Ethernet0/0/8
        3.3.3.3/32  ISIS-L2 15   20          D   40.0.0.1        Ethernet0/0/8
        4.4.4.4/32  ISIS-L2 15   10          D   40.0.0.1        Ethernet0/0/8
        5.5.5.5/32  Direct  0    0           D   127.0.0.1       LoopBack0
       10.0.0.0/30  ISIS-L2 15   30          D   40.0.0.1        Ethernet0/0/8
       10.0.2.0/30  ISIS-L2 15   30          D   40.0.0.1        Ethernet0/0/8
       20.0.0.0/30  ISIS-L2 15   20          D   40.0.0.1        Ethernet0/0/8
       30.0.0.0/30  ISIS-L2 15   20          D   40.0.0.1        Ethernet0/0/8
       40.0.0.0/30  Direct  0    0           D   40.0.0.2        Ethernet0/0/8
       40.0.0.2/32  Direct  0    0           D   127.0.0.1       Ethernet0/0/8
       40.0.0.3/32  Direct  0    0           D   127.0.0.1       Ethernet0/0/8
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0
127.255.255.255/32  Direct  0    0           D   127.0.0.1       InLoopBack0
255.255.255.255/32  Direct  0    0           D   127.0.0.1       InLoopBack0

ISIS cost for all interfaces is 10 by default. It can be changed manually by ‘isis cost‘ command.

Some other usefull maintenance commands:

[1]dis isis peer verbose

                          Peer information for ISIS(1)

  System Id     Interface          Circuit Id       State HoldTime Type     PRI (priority for DIS election)
-------------------------------------------------------------------------------
0020.0200.2002  Eth0/0/8           0020.0200.2002.03 Up   9s       L1       64

  MT IDs supported     : 0(UP) 
  Local MT IDs         : 0 
  Area Address(es)     : 10 
  Peer IP Address(es)  : 10.0.0.2        
  Uptime               : 03:04:27
  Adj Protocol         : IPV4 
  Restart Capable      : YES
  Suppressed Adj       : NO
  Peer System Id       : 0020.0200.2002  

Total Peer(s): 1

[1]display isis interface verbose 

                       Interface information for ISIS(1)
                       ---------------------------------
 Interface       Id      IPV4.State          IPV6.State      MTU  Type  DIS 
 Eth0/0/8        001         Up                 Down         1497 L1/L2 No/No 
  Circuit MT State            : Standard 
  Description                 : HUAWEI, AR Series, Ethernet0/0/8 Interface
  SNPA Address                : 00e0-fc03-2b68
  IP Address                  : 10.0.0.1
  IPV6 Link Local Address     :
  IPV6 Global Address(es)     :
  Csnp Timer Value            :  L1    10  L2    10
  Hello Timer Value           :  L1    10  L2    10
  DIS Hello Timer Value       :  L1     3  L2     3
  Hello Multiplier Value      :  L1     3  L2     3
  LSP-Throttle Timer          :  L12    50
  Cost                        :  L1    10  L2    10
  Ipv6 Cost                   :  L1    10  L2    10
  Priority                    :  L1    64  L2    64
  Retransmit Timer Value      :  L12    5
  Bandwidth-Value             :  Low  100000000  High          0
  Static Bfd                  :  NO
  Dynamic Bfd                 :  NO
  Fast-Sense Rpr              :  NO

 Interface       Id      IPV4.State          IPV6.State      MTU  Type  DIS   
 Loop0           001         Up                 Down         1500 L1/L2 -- 
  Circuit MT State            : Standard 
  Circuit Parameters          : passive 
  Description                 : HUAWEI, AR Series, LoopBack0 Interface
  SNPA Address                : 0000-0000-0000
  IP Address                  : 1.1.1.1
  IPV6 Link Local Address     :
  IPV6 Global Address(es)     :
  Csnp Timer Value            :  L12   10
  Hello Timer Value           :        10
  DIS Hello Timer Value       :
  Hello Multiplier Value      :         3
  Cost                        :  L1     0  L2     0
  Ipv6 Cost                   :  L1     0  L2     0
  Retransmit Timer Value      :  L12    5
  LSP-Throttle Timer          :  L12   50
  Bandwidth-Value             :  Low          0  High          0
  Static Bfd                  :  NO
  Dynamic Bfd                 :  NO
  Fast-Sense Rpr              :  NO

[1]dis isis error 

                    Statistics of error packets for ISIS(1)
                    ---------------------------------------
LSP packet errors:
Longer LSP              : 0           Smaller LSP             : 0           
Mismatched Level        : 0           Invalid Sysid           : 0           
Zero Sequence Number    : 0           Illegal IS Type         : 0           
Zero Checksum           : 0           Incorrect Checksum      : 0           
Bad Authentication      : 0           Bad Auth Count          : 0           
More Protocol TLV       : 0           Bad Nbr TLV             : 0           
Bad Extended IS TLV     : 0           Bad IF Addr TLV         : 0           
Bad Reach TLV           : 0           Bad Inter Domain TLV    : 0           
Mismatched Area Id(L1)  : 0           Bad TLV Length          : 0          
Bad Alias TLV           : 0           Bad Area TLV            : 0           
Bad SRLG TLV            : 0           Unknown Adjacency       : 0           
Bad Protocol ID         : 0           Bad Version             : 0           
Zero Lifetime           : 0           Bad Ext Reach TLV       : 0           
Bad TE Router ID TLV    : 0           Bad TE Sub TLV          : 0           

Hello packet errors:
Bad Packet Length       : 0           Reserved CircType       : 0           
Repeated System ID      : 0           Bad Circuit Type        : 0           
Longer packet           : 0           More Area Addr          : 0           
Longer Area Addr        : 0           Bad Area Addr TLV       : 0           
More IF Addr            : 0           Bad Formatted IF TLV    : 0           
More Nbr SNPA(LAN)      : 0           Invalid Sysid           : 0           
Bad TLV Length          : 0           Zero HoldingTime        : 0           
Unusable IP Addr        : 0           Repeated IPv4 Addr      : 0           
Mismatched Area Addr(L1): 0           Mismatched Proto        : 0           
SNPA Conflicted(LAN)    : 0           Mismatched Level        : 0           
Mismatched Max Area Addr: 0           Bad Authentication      : 0           
More Auth TLV           : 0           3-Way Option Error(P2P) : 0           
No Area Addr TLV        : 0           Bad Protocol ID         : 0           
Bad Version             : 0           Invalid IPv6 Addr       : 0           
More IPv6 IF Addr       : 0           Duplicate IPv6 Addr     : 0           
More Optional Checksum  : 0           Bad Optional Checksum   : 0           
--------------------------------------------------------------------

<1> debugging isis adjacency 

May  7 2013 16:17:06.629.1-05:13 1 ISIS/6/ISIS:
 ISIS-1-ADJ: Use level-1 IIH enconde cache to send IIH, Eth0/0/8.(IS15_2679)

May  7 2013 16:17:06.629.2-05:13 1 ISIS/6/ISIS:
 ISIS-1-ADJ: Sending Lan L1 Hello on Eth0/0/8, to SNPA 0180.c200.0014.(IS15_6941)

May  7 2013 16:17:07.319.1-05:13 1 ISIS/6/ISIS:
 ISIS-1-IIH: Set L1 holdtime on Eth0/0/8 for NBR 0020.0200.2002 as 9(IS21_968)

In this post I focused only on basic ISIS configuration. This protocol is widely used among ISPs. I will spend more time in the future to show you more functions and ISIS configuration examples.

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