Sub-interface vlan issues

[ahcadmin1]

We're replacing our 1841's with ISR 4321's.  We are running sub-interfaces on the uplink ports on both routers (e.g. - g0/0/0.1 -> data vlan, g0/0/0.100 -> voice vlan) on both the old and new routers.  Everything works fine on the new router until I add the second sub-interface and then the two stop talking... No ping response from switch.  The uplink on the switch is set to switchport mode trunk, and it is (almost) exactly the same config on both routers.  Also, I verified speed/duplex settings are matched... Tried auto and manually configuring both.

Switch -> WS-C2960-24TT-L

Old Router -> Cisco 1841

New Router -> Cisco ISR 4321

Anyone have any ideas?  I can upload the configs if needed... what's the best way to do that in the forum?

Thanks for your time,

Josh

[Reza Sharifi]

So, the first sub-interface works fine but I as soon as you add a second one both sub-interfaces stop working?

Can you post the config from the new router?

HTH

[ahcadmin1]

Correct.

!
hostname <hostname>
!
boot-start-marker
boot system flash bootflash:isr4300-universalk9.03.13.04.S.154-3.S4-ext.SPA.bin
boot-end-marker
!
!
vrf definition Mgmt-intf
!
address-family ipv4
exit-address-family
!
address-family ipv6
exit-address-family
!
card type t1 0 1
logging buffered warnings
enable secret
!
aaa new-model
!
!
aaa authentication login default local
!
!
!
!
!
aaa session-id common
no ip source-route
!
!
!
!
!
!
!
!
!
no ip domain lookup
ip domain name ahc.com

!
!
!
!
!
!
!
!
!
!
subscriber templating
!
multilink bundle-name authenticated
!
password encryption aes
!
!
!
license udi pid ISR4321/K9 sn FDO1949178B
!

!
redundancy
mode none
!
!
!
!
controller T1 0/1/0
framing esf
linecode b8zs
cablelength long 0db
channel-group 1 timeslots 1-24
!
controller T1 0/1/1
framing esf
linecode b8zs
cablelength long 0db
channel-group 1 timeslots 1-24
!
!
!
ip tcp synwait-time 10
!
class-map match-any REALTIME
match ip dscp cs5 ef
class-map match-any PRIORITY
match ip dscp cs2 af21 af22 af23
class-map match-any MISSIONCRITICAL
match ip dscp cs3 af31 af32 af33 cs6 cs7
class-map match-any INTERACTIVE
match ip dscp cs4 af41 af42 af43
class-map match-any Mark_af41
match access-group name af41
class-map match-any Mark_ef
match access-group name ef
class-map match-any Mark_af21
match access-group name af21
class-map match-any Mark_af31
match access-group name af31
!
policy-map CL-output
class REALTIME
priority percent 36
class INTERACTIVE
set ip dscp af41
bandwidth remaining percent 25
random-detect dscp-based
class MISSIONCRITICAL
set ip dscp af31
bandwidth remaining percent 25
random-detect dscp-based
class PRIORITY
set ip dscp af21
bandwidth remaining percent 25
random-detect dscp-based
class class-default
bandwidth remaining percent 25
random-detect dscp-based
fair-queue
policy-map 3M
class class-default
shape average 3000000
service-policy CL-output
policy-map qos-mark
class Mark_af21
set ip dscp af21
class Mark_af31
set ip dscp af31
class Mark_af41
set ip dscp af41
class Mark_ef
set ip dscp ef
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Multilink1
bandwidth 3000
ip address <public ip> 255.255.255.252
ppp multilink
ppp multilink group 1
ppp multilink fragment delay 500
service-policy output 3M
!
interface GigabitEthernet0/0/0
no ip address
negotiation auto
service-policy input qos-mark
!
interface GigabitEthernet0/0/0.1
description Reidsville Data LAN
encapsulation dot1Q 1 native
ip address <xxx.xxx.1.xxx> 255.255.255.0
no cdp enable
!
!
interface GigabitEthernet0/0/0.100
description Reidsville Data LAN
encapsulation dot1Q 100 native
ip address <xxx.xxx.100.xxx> 255.255.255.0
no cdp enable
!
interface GigabitEthernet0/0/1
no ip address
no negotiation auto
speed 1000
!
interface Serial0/1/0:1
bandwidth 3000
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1
!
interface Serial0/1/1:1
bandwidth 3000
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1
!
interface GigabitEthernet0
vrf forwarding Mgmt-intf
no ip address
shutdown
negotiation auto
!
router bgp xxxxx
bgp log-neighbor-changes
network <lan network>
neighbor xxx
!
ip forward-protocol nd
no ip http server
no ip http secure-server
ip tftp source-interface GigabitEthernet0
ip ssh rsa keypair-name ssh_key
ip ssh version 2
!

[acampbell · Accepted solution]

Hi,

Not sure if you have shown a typo.

You are making dotq .1 vlan 1 native

Then doing exactly the same dot1q .100

Which one do you want to be the native vlan , I would imagine it will be .1

So remove the line with native from .100

interface GigabitEthernet0/0/0.1
description Reidsville Data LAN
encapsulation dot1Q 1 native
ip address <xxx.xxx.1.xxx> 255.255.255.0
no cdp enable
!
!
interface GigabitEthernet0/0/0.100
description Reidsville Data LAN
encapsulation dot1Q 100 native  <-------------------OOPS
ip address <xxx.xxx.100.xxx> 255.255.255.0
no cdp enable
!

Regards

Alex

[ahcadmin1]

I figured this out shortly after posting the config, yes this was the issue.  I was copying and pasting and completely missed the native line.  Thanks so much for responding.