IS-IS configured over a trunk link between l3 switches

kpvnss · ‎04-10-2012

Hi,

I have got two switches s1 and s2 which are connected through a trunk port. SVIs are configured on two switches along with ISIS. Problem is switches are not able to route the SVIs or networks configured on other switches. I dont know if it can be done on trunk link, so I need help in this. I am copying the configuration of two switches:

This is the trunk link:

S1(3/3) <--->S2(7/1)

I have checked this scenario by making the the ports 3/3 and 7/1 on both switches as l3 ports and it was working fine. So just wanted to confirm if this can be done or not.

Switch 1

Switch#sh run

Building configuration...

Current configuration : 2852 bytes

!

! Last configuration change at 06:50:48 UTC Tue Apr 10 2012

!

version 15.1

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

service compress-config

!

hostname Switch

!

boot-start-marker

boot-end-marker

!

no aaa new-model

hw-module system max-queue-limit 7000

!

vtp domain cisco

vtp mode transparent

!

power redundancy-mode redundant

!

spanning-tree mode pvst

spanning-tree extend system-id

!

vlan internal allocation policy ascending

!

vlan 6-7,10,20,30

!

interface Loopback1

ip address 3.3.3.3 255.255.255.255

ip router isis

!

interface FastEthernet1

no ip address

shutdown

speed auto

duplex auto

!

interface TenGigabitEthernet1/1

!

interface TenGigabitEthernet1/2

!

interface GigabitEthernet1/3

!

interface GigabitEthernet1/4

!

interface GigabitEthernet1/5

!

interface GigabitEthernet1/6

!

interface GigabitEthernet3/1

!

interface GigabitEthernet3/2

!

interface GigabitEthernet3/3

switchport mode trunk

!

interface GigabitEthernet3/4

!

interface GigabitEthernet3/5

!

interface GigabitEthernet3/6

!

interface GigabitEthernet3/7

!

interface GigabitEthernet3/8

!

interface GigabitEthernet3/9

!

interface GigabitEthernet3/10

!

interface GigabitEthernet3/11

!

interface GigabitEthernet3/12

!

interface GigabitEthernet3/13

!

interface GigabitEthernet3/14

!

interface GigabitEthernet3/15

!

interface GigabitEthernet3/16

!

interface GigabitEthernet3/17

!

interface GigabitEthernet3/18

!

interface GigabitEthernet3/19

!

interface GigabitEthernet3/20

!

interface GigabitEthernet3/21

!

interface GigabitEthernet3/22

!

interface GigabitEthernet3/23

!

interface GigabitEthernet3/24

!

interface GigabitEthernet3/25

!

interface GigabitEthernet3/26

!

interface GigabitEthernet3/27

!

interface GigabitEthernet3/28

!

interface GigabitEthernet3/29

!

interface GigabitEthernet3/30

!

interface GigabitEthernet3/31

!

interface GigabitEthernet3/32

!

interface GigabitEthernet3/33

!

interface GigabitEthernet3/34

!

interface GigabitEthernet3/35

!

interface GigabitEthernet3/36

!

interface GigabitEthernet3/37

!

interface GigabitEthernet3/38

!

interface GigabitEthernet3/39

!

interface GigabitEthernet3/40

!

interface GigabitEthernet3/41

!

interface GigabitEthernet3/42

!

interface GigabitEthernet3/43

!

interface GigabitEthernet3/44

!

interface GigabitEthernet3/45

!

interface GigabitEthernet3/46

!

interface GigabitEthernet3/47

!

interface GigabitEthernet3/48

!

interface Vlan1

no ip address

!

interface Vlan10

ip address 10.0.0.2 255.0.0.0

ip router isis

!

interface Vlan30

ip address 30.0.0.1 255.0.0.0

ip router isis

!

router isis

net 49.0001.0000.0000.000c.00

nsf cisco

nsf interval 0

nsf interface wait 30

maximum-paths 8

!

no ip http server

!

line con 0

stopbits 1

speed 38400

line vty 0 4

login

!

end

Switch#

Switch 2

Switch#sh run

Building configuration...

Current configuration : 4604 bytes

!

! Last configuration change at 04:45:49 UTC Tue Apr 10 2012

!

version 15.1

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

service compress-config

!

hostname Switch

!

boot-start-marker

boot-end-marker

!

no aaa new-model

!

ip vrf mgmtVrf

!

vtp domain cisco

vtp mode transparent

!

power redundancy-mode redundant

!

spanning-tree mode pvst

spanning-tree extend system-id

!

redundancy

mode sso

!

vlan internal allocation policy ascending

!

vlan 7-11,14-15,20,30

!

interface Loopback0

no ip address

!

interface Loopback1

ip address 1.1.1.1 255.255.255.255

ip router isis

!

interface FastEthernet1

ip vrf forwarding mgmtVrf

no ip address

speed auto

duplex auto

!

interface GigabitEthernet1/1

!

interface GigabitEthernet1/2

!

interface GigabitEthernet1/3

!

interface GigabitEthernet1/4

!

interface GigabitEthernet1/5

!

interface GigabitEthernet1/6

!

interface GigabitEthernet1/7

!

interface GigabitEthernet1/8

!

interface GigabitEthernet1/9

!

interface GigabitEthernet1/10

!

interface GigabitEthernet1/11

!

interface GigabitEthernet1/12

!

interface GigabitEthernet1/13

!

interface GigabitEthernet1/14

!

interface GigabitEthernet1/15

!

interface GigabitEthernet1/16

!

interface GigabitEthernet1/17

!

interface GigabitEthernet1/18

!

interface GigabitEthernet1/19

!

interface GigabitEthernet1/20

!

interface GigabitEthernet1/21

!

interface GigabitEthernet1/22

!

interface GigabitEthernet1/23

!

interface GigabitEthernet1/24

!

interface GigabitEthernet1/25

!

interface GigabitEthernet1/26

!

interface GigabitEthernet1/27

!

interface GigabitEthernet1/28

!

interface GigabitEthernet1/29

!

interface GigabitEthernet1/30

!

interface GigabitEthernet1/31

!

interface GigabitEthernet1/32

!

interface GigabitEthernet1/33

!

interface GigabitEthernet1/34

!

interface GigabitEthernet1/35

!

interface GigabitEthernet1/36

!

interface GigabitEthernet1/37

!

interface GigabitEthernet1/38

!

interface GigabitEthernet1/39

!

interface GigabitEthernet1/40

!

interface GigabitEthernet1/41

!

interface GigabitEthernet1/42

!

interface GigabitEthernet1/43

!

interface GigabitEthernet1/44

!

interface GigabitEthernet1/45

!

interface GigabitEthernet1/46

!

interface GigabitEthernet1/47

!

interface GigabitEthernet1/48

!

interface TenGigabitEthernet3/1

!

interface TenGigabitEthernet3/2

!

interface GigabitEthernet3/3

!

interface GigabitEthernet3/4

!

interface GigabitEthernet3/5

!

interface GigabitEthernet3/6

!

interface TenGigabitEthernet4/1

!

interface TenGigabitEthernet4/2

!

interface GigabitEthernet4/3

!

interface GigabitEthernet4/4

!

interface GigabitEthernet4/5

!

interface GigabitEthernet4/6

!

interface GigabitEthernet7/1

switchport mode trunk

!

interface GigabitEthernet7/2

!

interface GigabitEthernet7/3

!

interface GigabitEthernet7/4

!

interface GigabitEthernet7/5

!

interface GigabitEthernet7/6

!

interface GigabitEthernet7/7

!

interface GigabitEthernet7/8

!

interface GigabitEthernet7/9

!

interface GigabitEthernet7/10

!

interface GigabitEthernet7/11

!

interface GigabitEthernet7/12

!

interface GigabitEthernet7/13

!

interface GigabitEthernet7/14

!

interface GigabitEthernet7/15

!

interface GigabitEthernet7/16

!

interface GigabitEthernet7/17

!

interface GigabitEthernet7/18

!

interface GigabitEthernet7/19

!

interface GigabitEthernet7/20

!

interface GigabitEthernet7/21

!

interface GigabitEthernet7/22

!

interface GigabitEthernet7/23

!

interface GigabitEthernet7/24

!

interface GigabitEthernet7/25

!

interface GigabitEthernet7/26

!

interface GigabitEthernet7/27

!

interface GigabitEthernet7/28

!

interface GigabitEthernet7/29

!

interface GigabitEthernet7/30

!

interface GigabitEthernet7/31

!

interface GigabitEthernet7/32

!

interface GigabitEthernet7/33

!

interface GigabitEthernet7/34

!

interface GigabitEthernet7/35

!

interface GigabitEthernet7/36

!

interface GigabitEthernet7/37

!

interface GigabitEthernet7/38

!

interface GigabitEthernet7/39

!

interface GigabitEthernet7/40

!

interface GigabitEthernet7/41

!

interface GigabitEthernet7/42

!

interface GigabitEthernet7/43

!

interface GigabitEthernet7/44

!

interface GigabitEthernet7/45

!

interface GigabitEthernet7/46

!

interface GigabitEthernet7/47

!

interface GigabitEthernet7/48

!

interface Vlan1

no ip address

!

interface Vlan10

ip address 10.0.0.1 255.0.0.0

ip router isis

!

interface Vlan20

ip address 20.0.0.1 255.0.0.0

ip router isis

!

router isis

net 49.0001.0000.0000.000b.00

nsf cisco

nsf interval 0

nsf interface wait 30

maximum-paths 8

!

no ip http server

!

line con 0

stopbits 1

speed 38400

line vty 0 4

login

!

end

Switch#

Thanks,

Krishna,

Employee Id:-496777,

Cisco Systems, Inc,

Bangalore.

Kyle McKay · ‎04-13-2012

Does a routing adjacency establish between the two routers?

If I am understanding you correctly, the issue is that you cannot route to the other switch from the local switch - meaning you are not recieving routes from the neighbor ?

kpvnss · ‎04-13-2012

Yes Kyle I am not recieving routes from the neighbor

kpvnss · ‎04-13-2012

Kyle I forgot to mention something If I configure the ports that are linked between the switches as access ports adding them to some vlan and configure SVI on both of the switches for that particular vlan and also configure ISIS on this SVI and remaining SVIs/L3 ports, I am able to see the routes of neighbouring switch. I could see problem only with configuring the ports as trunk.

Reza Sharifi · ‎04-13-2012

I know your ports are trunked and therefore all vlans are allowed, but can you add the specific vlans and test again?

kpvnss · ‎04-15-2012

Yes Reza I did that using "sw trunk allowed ", but not able to see the routes of another switch.

Peter Paluch · ‎04-15-2012

Reza, Krisha,

Please allow me to join the discussion. This is an interesting issue.

Krisha, can you please provide the output of the following commands from both switches? It's going to be quite a list but possibly it will help us narrow down the scope of the problem.

show cdp neighbor
show interfaces trunk
show isis neighbors
show clns
show clns protocol
show clns neighbors
show ip protocols
show ip route

Thank you!

Best regards,

Peter

kpvnss · ‎04-15-2012

Peter, I am sending you the info which you asked me.

Switch 1:-

s1#sh cdp neigh

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

gsgsw-labswitch16

Fas 1 162 R S I WS-C4948 Gig 1/13

s2 Gig 3/1 127 R S I WS-C4503- Gig 3/1

s1#sh run int gi3/1

Building configuration...

Current configuration : 93 bytes

!

interface GigabitEthernet3/1

switchport trunk allowed vlan 10

switchport mode trunk

end

s1#sh ip int br | i up

FastEthernet1 unassigned YES unset up up

GigabitEthernet3/1 unassigned YES unset up up

GigabitEthernet3/2 unassigned YES unset up up

GigabitEthernet3/3 unassigned YES unset up up

GigabitEthernet3/4 unassigned YES unset up up

Loopback1 1.1.1.1 YES manual up up

Vlan1 unassigned YES unset up up

Vlan10 10.0.0.1 YES manual up up

Vlan20 20.0.0.1 YES manual up up

s1#sh inter

s1#sh interfaces tru

s1#sh interfaces trunk

Port Mode Encapsulation Status Native vlan

Gi3/1 on 802.1q trunking 1

Port Vlans allowed on trunk

Gi3/1 10

Port Vlans allowed and active in management domain

Gi3/1 10

Port Vlans in spanning tree forwarding state and not pruned

Gi3/1 10

s1#sh

s1#show isi

s1#show isis neigh

s1#show isis neighbors

System Id Type Interface IP Address State Holdtime Circuit Id

s1#sh

s1#show clsn

s1#show clns

Global CLNS Information:

3 Interfaces Enabled for CLNS

Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime 64

ERPDU's requested on locally generated packets

Running IS-IS in IP-only mode (CLNS forwarding not allowed)

NET: 49.0001.0002.0002.0002.00

s1#sh clns proto

s1#sh clns protocol

IS-IS Router: 2

System Id: 0002.0002.0002.00 IS-Type: level-1-2

Manual area address(es):

49.0001

Routing for area address(es):

49.0001

Interfaces supported by IS-IS:

Loopback1 - IP

Vlan20 - IP

Vlan10 - IP

Redistribute:

static (on by default)

Distance for L2 CLNS routes: 110

RRR level: none

Generate narrow metrics: level-1-2

Accept narrow metrics: level-1-2

Generate wide metrics: none

Accept wide metrics: none

s1#sh

s1#show clns

s1#show clns neigh

s1#show clns neighbors

System Id Interface SNPA State Holdtime Type Protocol

s1#sh ip protocols

*** IP Routing is NSF aware ***

Routing Protocol is "isis 2"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Redistributing: isis 2

Address Summarization:

None

Maximum path: 4

Routing for Networks:

Vlan10

Vlan20

Loopback1

Routing Information Sources:

Gateway Distance Last Update

Distance: (default is 115)

s1#sh ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback1

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.0.0.0/8 is directly connected, Vlan10

L 10.0.0.1/32 is directly connected, Vlan10

20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 20.0.0.0/8 is directly connected, Vlan20

L 20.0.0.1/32 is directly connected, Vlan20

s1#

Switch 2:-

s2#sh cdp neigh

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

s1 Gig 3/1 122 R S I WS-C4503 Gig 3/1

s2#sh run int gi3/1

Building configuration...

Current configuration : 93 bytes

!

interface GigabitEthernet3/1

switchport trunk allowed vlan 10

switchport mode trunk

end

s2#sh ip int br | i up

GigabitEthernet3/1 unassigned YES unset up up

GigabitEthernet3/2 unassigned YES unset up up

GigabitEthernet3/3 unassigned YES unset up up

GigabitEthernet3/4 unassigned YES unset up up

Loopback1 2.2.2.2 YES manual up up

Vlan1 unassigned YES unset up up

Vlan10 10.0.0.2 YES NVRAM up up

Vlan30 30.0.0.1 YES manual up up

s2#sh inter

s2#sh interfaces tru

s2#sh interfaces trunk

Port Mode Encapsulation Status Native vlan

Gi3/1 on 802.1q trunking 1

Port Vlans allowed on trunk

Gi3/1 10

Port Vlans allowed and active in management domain

Gi3/1 10

Port Vlans in spanning tree forwarding state and not pruned

Gi3/1 10

s2#sh

s2#show isi

s2#show isis neig

s2#show isis neighbors

System Id Type Interface IP Address State Holdtime Circuit Id

s2#sh

s2#show clns

Global CLNS Information:

3 Interfaces Enabled for CLNS

Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime 64

ERPDU's requested on locally generated packets

Running IS-IS in IP-only mode (CLNS forwarding not allowed)

NET: 49.0001.0001.0001.0001.00

s2#sh clns pro

s2#sh clns protocol

IS-IS Router: 2

System Id: 0001.0001.0001.00 IS-Type: level-1-2

Manual area address(es):

49.0001

Routing for area address(es):

49.0001

Interfaces supported by IS-IS:

Loopback1 - IP

Vlan30 - IP

Vlan10 - IP

Redistribute:

static (on by default)

Distance for L2 CLNS routes: 110

RRR level: none

Generate narrow metrics: level-1-2

Accept narrow metrics: level-1-2

Generate wide metrics: none

Accept wide metrics: none

s2#sh

s2#show clns

s2#show clns neigh

s2#show clns neighbors

System Id Interface SNPA State Holdtime Type Protocol

s2#sh ip

s2#sh ip pro

s2#sh ip protocols

*** IP Routing is NSF aware ***

Routing Protocol is "isis 2"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Redistributing: isis 2

Address Summarization:

None

Maximum path: 4

Routing for Networks:

Vlan10

Vlan30

Loopback1

Routing Information Sources:

Gateway Distance Last Update

Distance: (default is 115)

s2#sh ip

s2#sh ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

2.0.0.0/32 is subnetted, 1 subnets

C 2.2.2.2 is directly connected, Loopback1

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.0.0.0/8 is directly connected, Vlan10

L 10.0.0.2/32 is directly connected, Vlan10

30.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 30.0.0.0/8 is directly connected, Vlan30

L 30.0.0.1/32 is directly connected, Vlan30

s2#

kpvnss · ‎04-16-2012

Hi Peter,

Another small thing which I wanted to mention if I make the ports which are linked between switch 1 and switch 2 as access instead of trunk then everything works fine, I am sending you the required info for that also please look into it.

Switch 1:-

s1#sh cdp neigh

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

gsgsw-labswitch16

Fas 1 179 R S I WS-C4948 Gig 1/13

s2 Gig 3/1 144 R S I WS-C4503- Gig 3/1

s1#sh run int gi3/1

Building configuration...

Current configuration : 87 bytes

!

interface GigabitEthernet3/1

switchport access vlan 10

switchport mode access

end

s1#sh ip int br | i up

FastEthernet1 unassigned YES unset up up

GigabitEthernet3/1 unassigned YES unset up up

GigabitEthernet3/2 unassigned YES unset up up

GigabitEthernet3/3 unassigned YES unset up up

GigabitEthernet3/4 unassigned YES unset up up

Loopback1 1.1.1.1 YES manual up up

Vlan1 unassigned YES unset up up

Vlan10 10.0.0.1 YES manual up up

Vlan20 20.0.0.1 YES manual up up

s1#sh isis niegh

s1#sh isis neigh

s1#sh isis neighbors

System Id Type Interface IP Address State Holdtime Circuit Id

s2 L1 Vl10 10.0.0.2 UP 8 s2.01

s2 L2 Vl10 10.0.0.2 UP 8 s2.01

s1#sh clns

Global CLNS Information:

3 Interfaces Enabled for CLNS

Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime 64

ERPDU's requested on locally generated packets

Running IS-IS in IP-only mode (CLNS forwarding not allowed)

NET: 49.0001.0002.0002.0002.00

s1#sh clns proto

s1#sh clns protocol

IS-IS Router: 2

System Id: 0002.0002.0002.00 IS-Type: level-1-2

Manual area address(es):

49.0001

Routing for area address(es):

49.0001

Interfaces supported by IS-IS:

Loopback1 - IP

Vlan20 - IP

Vlan10 - IP

Redistribute:

static (on by default)

Distance for L2 CLNS routes: 110

RRR level: none

Generate narrow metrics: level-1-2

Accept narrow metrics: level-1-2

Generate wide metrics: none

Accept wide metrics: none

s1#sh clns neigh

System Id Interface SNPA State Holdtime Type Protocol

s2 Vl10 0021.d8ce.51ff Up 8 L1L2 IS-IS

s1#sh ip proto

s1#sh ip protocols

*** IP Routing is NSF aware ***

Routing Protocol is "isis 2"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Redistributing: isis 2

Address Summarization:

None

Maximum path: 4

Routing for Networks:

Vlan10

Vlan20

Loopback1

Routing Information Sources:

Gateway Distance Last Update

2.2.2.2 115 00:06:19

Distance: (default is 115)

s1#sh ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback1

2.0.0.0/32 is subnetted, 1 subnets

i L1 2.2.2.2 [115/20] via 10.0.0.2, 00:07:25, Vlan10

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.0.0.0/8 is directly connected, Vlan10

L 10.0.0.1/32 is directly connected, Vlan10

20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 20.0.0.0/8 is directly connected, Vlan20

L 20.0.0.1/32 is directly connected, Vlan20

i L1 30.0.0.0/8 [115/20] via 10.0.0.2, 00:07:25, Vlan10

s1#

Switch 2:-

s2#

s2#sh cdp neigh

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

s1 Gig 3/1 160 R S I WS-C4503 Gig 3/1

s2#sh run int gi3/1

Building configuration...

Current configuration : 87 bytes

!

interface GigabitEthernet3/1

switchport access vlan 10

switchport mode access

end

s2#sh ip int br | i up

GigabitEthernet3/1 unassigned YES unset up up

GigabitEthernet3/2 unassigned YES unset up up

GigabitEthernet3/3 unassigned YES unset up up

GigabitEthernet3/4 unassigned YES unset up up

Loopback1 2.2.2.2 YES manual up up

Vlan1 unassigned YES unset up up

Vlan10 10.0.0.2 YES NVRAM up up

Vlan30 30.0.0.1 YES manual up up

s2#sh isis neigh

System Id Type Interface IP Address State Holdtime Circuit Id

s1 L1 Vl10 10.0.0.1 UP 24 s2.01

s1 L2 Vl10 10.0.0.1 UP 29 s2.01

s2#sh clns

Global CLNS Information:

3 Interfaces Enabled for CLNS

Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime 64

ERPDU's requested on locally generated packets

Running IS-IS in IP-only mode (CLNS forwarding not allowed)

NET: 49.0001.0001.0001.0001.00

s2#sh clns

s2#sh clns neig

s2#sh clns pro

s2#sh clns protocol

IS-IS Router: 2

System Id: 0001.0001.0001.00 IS-Type: level-1-2

Manual area address(es):

49.0001

Routing for area address(es):

49.0001

Interfaces supported by IS-IS:

Loopback1 - IP

Vlan30 - IP

Vlan10 - IP

Redistribute:

static (on by default)

Distance for L2 CLNS routes: 110

RRR level: none

Generate narrow metrics: level-1-2

Accept narrow metrics: level-1-2

Generate wide metrics: none

Accept wide metrics: none

s2#sh clns

s2#sh clns neigh

System Id Interface SNPA State Holdtime Type Protocol

s1 Vl10 000d.ed4a.49ff Up 29 L1L2 IS-IS

s2#sh ip pro

s2#sh ip protocols

*** IP Routing is NSF aware ***

Routing Protocol is "isis 2"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Redistributing: isis 2

Address Summarization:

None

Maximum path: 4

Routing for Networks:

Vlan10

Vlan30

Loopback1

Routing Information Sources:

Gateway Distance Last Update

1.1.1.1 115 00:00:03

Distance: (default is 115)

s2#sh ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

1.0.0.0/32 is subnetted, 1 subnets

i L1 1.1.1.1 [115/20] via 10.0.0.1, 00:09:00, Vlan10

2.0.0.0/32 is subnetted, 1 subnets

C 2.2.2.2 is directly connected, Loopback1

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.0.0.0/8 is directly connected, Vlan10

L 10.0.0.2/32 is directly connected, Vlan10

i L1 20.0.0.0/8 [115/20] via 10.0.0.1, 00:09:00, Vlan10

30.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 30.0.0.0/8 is directly connected, Vlan30

L 30.0.0.1/32 is directly connected, Vlan30

s2#

Thanks,

Krishna.

Peter Paluch · ‎04-16-2012

Hello Krishna,

I will go over your outputs in more detail later today - thanks for uploading them.

The difference in the behavior caused by the trunk reminds me of a possible problem related to system MTU. Can you please enter the following command on the interface Vlan10 on both switches and see if it makes the IS-IS work through the trunk?

interface Vlan 10

no isis hello padding

Thank you!

Best regards,

Peter

kpvnss · ‎04-16-2012

Hi Peter,

I checked it by adding "no isis hello padding" this to the "int vlan 10" of both switches. Still it is not working...

Thanks,

krishna.

Peter Paluch · ‎04-16-2012

Hello Krishna,

I'd say it's time to do some debugging

Set the ports between the switches to access mode, and issue the debug isis adj-packets and debug isis protocol-errors. Observe the buildup of the adjacency and possibly record the sequence of steps taken for the routers to become adjacent.

Then, set the ports between the switches to trunk mode and again, observe the debug output. Try to find the spot where the debug begins to differ.

Best regards,

Peter

kpvnss · ‎04-16-2012

Hi Peter,

After changing the native vlan of trunk ports using (sw trunk native vlan 10), I could see the routes and ISIS is working fine.

interface GigabitEthernet3/1

switchport trunk native vlan 10

switchport trunk allowed vlan 10

switchport mode trunk

end

Thanks a lot everyone :-)

Regards,

krishna.

Peter Paluch · ‎04-17-2012

Krishna,

Thank you for updating us! But frankly, the solution does not make any sense Why should a native VLAN modification cause the IS-IS to miraculously start working?

I am suspecting some problem with STP here. Can you put back the native VLAN 1, wait 20-30 seconds, and check the output of show spanning-tree and show spanning-tree inconsistentports if there is any issue related to some STP-discovered inconsistency?

Once again, this solution is weird - and we've got to know the exact mechanism behind it.

Best regards,

Peter

kpvnss · ‎04-18-2012

Hi Peter,

I tested it and I am sure that this is not the problem of Spanning tree protocol. What I understand from my knowledge and after discussing with my teammates that as we need atleast one l3 channel on the top of which we can configure a routing protocol so that the routes can be exchanged using that l3 channel.

In my setup the intention was to create an SVI for vlan 10 on both of the switches which resembles configuring l3 interfaces between the switches. As we know that it is working fine if I make it as access port of the vlan 10. Problems come with trunk port whose default native vlan is 1, and all the untagged packets(including the packets which carry is-is routes info) are tagged with vlan 1, which shouldn't be the case and get dropped at other switch as there is no virtual l3 channel configured on vlan 1(i.e., configuring SVIs for vlan 1 at both ends), as we are creating a virtual l3 channel using SVIs of vlan 10. So if we change the native vlan of the trunk to vlan 10, the untagged packets will be tagged with vlan 10 info and as the SVIs are configured at both ends, routing info is exchanged and it is working successfully.

I hope that this makes sense. Once again thank you very much Peter.

Thanks,

Krishna.