ISIS Protocol - Level 2

Notes on ISIS - General Protocol Information

My notes on ISIS... Its general information picked from other websites too.. 

Topology

ISIS - General Protocol Info -

PDUs and Protocol Details

Hello -  To discover neighbours. 3 way handshake is performed to form adjacency. Address-family should be same inorder to form adjacency.

L2 LSP - Link state - Exchange of route information : Link-state id, sequence number, area, interfaces, protocols supported, ipv4 internal reachability,[ if configured] ipv6     reachability.

CSNP - Complete Sequence Number

PSNP - Partial Sequence Number

Category	Packet Type	Type Number
Hello	LAN Level-1 Hello	15
	LAN Level-2 Hello	16
	Point-to-point Hello	17
LSP	Level-1 LSP	18
	Level-2 LSP	20
SNP	Level-1 Complete SNP	24
	Level-2 Complete SNP	25
	Level-1 Partial SNP	26
	Level-2 Partial SNP	27

Packet Captures - This gives info related to all the packet captures.



TLVs

Padding - 08 type , length - ff - value can be zero or some pattern

Protocols supported - 81 , length - 02 , values - v4, v6 typically

Area Address - 01 , value - 04 bytes, values - something like 49.0001 kinds where 49  denotes private scheme in ISO standard

IPv4 Address - 84 , value - 4 - v4 Address of the interface where ISIS is enabled

IPv6 Address - e8 , value - 16 - v6 address of the interface  

ISIS Neighbor - 06 , value - 6 bytes - MAC/SNAP address of the interface - typically the mac remains same for all the interface on a router

Extend ISIS reach-ability - 16 , value - list of all ISIS neighbors MAC address 

Hostname - 7 , value - Name of the host - this is like DNS

LSP Entry in CSNP - 09 , Value  - Contains max 240 bytes data of all the LSPs it knows
IS-Reachability - 12 , value - Neighbor sys-id address and its metric

Flag Types

Partition repair -

Attached bits -

Overload bit - Doesn't take part in SPF calculation on other routers. As the router might not have all the routes/LSP. The router will be only included for connected routes.

IS type -value -  3 means - level2

Troubleshooting Details

CLIs

show isis neighbors : The adjacent neighbour info can be seen here. SNPA, local interface, state, hold-time , neighbors system-id

show isis summary : Details about the local systemid, internal, external preference, area which its part of, address-family support, is-type, lsdb

show isis interface  : All the interfaces which are part of ISIS gets displayed here. Options help to find if specific interface is part of the ISIS or not. Default timers are not displayed here.

show isis database : All the database info - LSP Id, sequence number , age , flags gets displayed. With detail , we get to know about system id, routes reachability, neighbor info, interfaces , area etc

show ip route summary : Gives info on the number of ISIS routes

show ip route isis : All the routes related to ISIS is displayed

show run all interface : Provides info on all the default Timers for that specific interface

logging console 7 , terminal monitor - prints all the ISIS logs and also other logs . Currently the choice of only ISIS is not present

Logging Info means

Mar 12 00:16:48 sc213 Rib: %ISIS-4-ISIS_L2_DISCHG Intf: vlan12, Elected self as DIS, priority 64
Desc : The router has elected self for vlan 12 - Based on priority number or system-id

Mar 12 00:16:48 sc213 Rib: %ISIS-4-ISIS_ADJCHG:Neighbor State Change for SystemID 4455.6677.88c9 on vlan15 to UP
Desc : The Neigbhor systemid with 88c9 on vlan 15 has come up. With qt traces one can see the transitions of states - Like INIT to UP etc

Mar 12 00:16:49 sc213 Rib: %ISIS-4-ISIS_L2_DISCHG Intf: vlan53, Resigned as DIS priority 64, Elected sysid 4455.6677.88ef, priority 86
Desc : The EOS router resigned as DIS on vlan 53 and elected 88ef as DIS as it has higher priority

ISIS RECV: l2-psn  source id doesn't match adjacencies
Desc : This is seen when source id inside l2-psn pdu system-id info does not match with already formed adjacency system-id info. 

Mar 12 01:27:54 sc213 Rib: ISIS RECV: l2-csn source id doesn't match adjacencies
Desc : Same as above , but this is with CSN instead of PSN. 

 

Basic Configuration

interface Port-Channel1

   mtu 5000

   switchport mode trunk

   ip proxy-arp

   ip address 200.8.8.1/24

   arp timeout 60

   isis enable 4294967294

   isis priority 3

   isis hello-interval 90

router isis 4294967294

   net 48.0000.1111.ffff.00

   is-type level-2

   log-adjacency-changes

   redistribute connected

   redistribute static

   address-family ipv4 unicast

Glances - Linux tool to grab lots of stats in one go...

Glances

As the name suggests, it provides a glance of the current system state/stat.

It covers most of the information related to a Linux system. CPU, Network, Disk, Mount points, Process.

To Install on Ubuntu:

sudo apt-get install python-pip build-essential python-dev
sudo pip install Glances
sudo pip install PySensors

To run :

sudks@sudks-ThinkPad-T420:~$ glances 

It provides output in form of html or csv etc.

In my case - apache2 is already installed.

sudks@sudks-ThinkPad-T420:~$ sudo mkdir /var/www/monitor

sudks@sudks-ThinkPad-T420:/var/www/monitor$ glances -o HTML -f /var/www/monitor/

Refer man page for more info.