subinterfaces - should i be able to ping it?

silly question, should i be able to ping a subinterface?
i have the following config:

1841#sh run
Building configuration...

Current configuration : 1287 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname 1841
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
ip subnet-zero
--More--
!
!
no ip dhcp use vrf connected
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.2
encapsulation dot1Q 2
ip address 10.1.21.1 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/0.3
encapsulation dot1Q 3
ip address 10.1.21.33 255.255.255.224
no snmp trap link-status
--More--
!
interface FastEthernet0/0.4
encapsulation dot1Q 4
ip address 10.1.21.65 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/0.5
encapsulation dot1Q 5
ip address 10.1.21.129 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/0.6
encapsulation dot1Q 6
ip address 10.1.21.193 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
--More--
no ip address
shutdown
clockrate 2000000
!
ip classless
!
ip http server
!
!
control-plane
line con 0
logging synchronous
line aux 0
line vty 0 4
login
!
end

i have a laptop plugged into the same switch as the router, with ip address of:
10.1.21.2 255.255.255.224
gateway 10.1.21.1

and i cant ping the subinterface 10.1.21.1

even from the router i cant ping the laptop 10.1.21.2...

this seems to simple its embarrassing... can anyone help?

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Comments

markzab

Might be a bit simple but are you sure you're using the correct cable to go from the laptop to the switch? Can you ping any of the other IP addresses or are you just having a problem with the default gateway address?

rakem

Its just the default gateway address. I have 2 other devices connected to the switch which i can ping from the laptop. I can ping the switch from the latop and other devices but cant ping the gateway from any device.

i should elaborate... im trying to setup some VLANs in a test lab, i cannot get devices on different VLANs to communicate, devices in the same vlan communicate fine but not different VLANs.

This obviously is a router problem since communication between vlans requires a layer 3 device... but as far as i can see my config on the router is good.

GeorgeMcFly22

Is your switch-port that connects to the router configured as trunk?

rakem

um i know it should be, but its a dell switch and im having troubling finding out how to check.

tech-airman

rakem wrote:

silly question, should i be able to ping a subinterface?
i have the following config:

1841#sh run
Building configuration...

Current configuration : 1287 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname 1841
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
ip subnet-zero
--More--
!
!
no ip dhcp use vrf connected
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.2
encapsulation dot1Q 2
ip address 10.1.21.1 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/0.3
encapsulation dot1Q 3
ip address 10.1.21.33 255.255.255.224
no snmp trap link-status
--More--
!
interface FastEthernet0/0.4
encapsulation dot1Q 4
ip address 10.1.21.65 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/0.5
encapsulation dot1Q 5
ip address 10.1.21.129 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/0.6
encapsulation dot1Q 6
ip address 10.1.21.193 255.255.255.224
no snmp trap link-status
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
--More--
no ip address
shutdown
clockrate 2000000
!
ip classless
!
ip http server
!
!
control-plane
line con 0
logging synchronous
line aux 0
line vty 0 4
login
!
end

i have a laptop plugged into the same switch as the router, with ip address of:
10.1.21.2 255.255.255.224
gateway 10.1.21.1

and i cant ping the subinterface 10.1.21.1

even from the router i cant ping the laptop 10.1.21.2...

this seems to simple its embarrassing... can anyone help?

rakem,

For 802.1q VLAN encapsulation, you need to assign an IP address to the main interface, in this case fa0/0, for the native VLAN.

DirtySouth

tech-airman wrote:

rakem,

For 802.1q VLAN encapsulation, you need to assign an IP address to the main interface, in this case fa0/0, for the native VLAN.

Actually, if you're doing trunking on a router interface with sub-interfaces, you do NOT want to assign an IP address to the physical interface. I believe this is true for IOS 12.2 & up. You only want to address the sub-interfaces. However, you do need to make sure you do a "No Shutdown" on the physical interface.

Rakem,
Yes, you should be able to ping the sub-interfaces. You'll need to figure out how to setup trunking on that Dell switch. If it were a Cisco Catalyst 2950 switch, you'd use the "switchport mode trunk" command on the trunking port of the switch.

spicc7

I am with DirtySouth on this one. It looks like the physical interface hasn't been brought up. Do a "no shutdown" on the physical interface and a "sh int" to verify the status of the interfaces.

georgemc

Also, the port your laptop is plugged into should be in VLAN2 as configured on the router. If a Dell switch defaults the same as a Cisco then it's probaby in vlan1. Does it even support vlan's?

tech-airman

DirtySouth wrote:

tech-airman wrote:

rakem,

For 802.1q VLAN encapsulation, you need to assign an IP address to the main interface, in this case fa0/0, for the native VLAN.

Actually, if you're doing trunking on a router interface with sub-interfaces, you do NOT want to assign an IP address to the physical interface. I believe this is true for IOS 12.2 & up. You only want to address the sub-interfaces. However, you do need to make sure you do a "No Shutdown" on the physical interface.

Rakem,
Yes, you should be able to ping the sub-interfaces. You'll need to figure out how to setup trunking on that Dell switch. If it were a Cisco Catalyst 2950 switch, you'd use the "switchport mode trunk" command on the trunking port of the switch.

DirtySouth,

According to Wendell Odom, CCIE #1624, in his book "CCNA Self-Study CCNA ICND Exam Certification Guide", page 309, Example 8-7 - Router Configuration for the 802.1Q Encapsulation Show in Figure 8-19 states:

interface fastethernet 0
ip address 10.1.1.1 255.255.255.0
!
interface fastethernet 0.2
ip address 10.1.2.1 255.255.255.0
encapsulation dot1q 2
!
interface fastethernet 0.3
ip address 10.1.3.1 255.255.255.0
encapsulation dot1q 3

Odom states after Example 8-7 that "The router IP address in the subnet of the 802.1Q native VLAN is configured on the physical interface instead of the subinterface...Also note that for the native VLAN, VLAN 1 in this case, the encapsulation command should not be used, or the router will encapuslate frames in an 802.1Q header."

So I'm going to follow what Odom says about assigning an IP address to the physical interface for 802.1Q trunk routing.

Source:

CCNA ICND Exam Certification Guide (CCNA Self-Study, 640-811, 640-801) - http://www.ciscopress.com/bookstore/product.asp?isbn=158720083X&rl=1

georgemc

rakem,
Yes, tech-airman is right about assigning an ip address to the physical port for 802.1q, but that is not relevant to that problem you are having. You want to ping a subinterface, specificall the subinterface that supports the subnet for VLAN2 as shown below.

rakem wrote:

!
interface FastEthernet0/0.2
encapsulation dot1Q 2
ip address 10.1.21.1 255.255.255.224
no snmp trap link-status

rakem wrote:

i have a laptop plugged into the same switch as the router, with ip address of:
10.1.21.2 255.255.255.224
gateway 10.1.21.1

and i cant ping the subinterface 10.1.21.1

With no additional/special configuration done to your switch, it will be in vlan1. Any machine plugged into the switch will only be able to ping machines in the same subnet. Without trunking turned on it will only be able to ping the physical port(if it has the correct IP) of the router. The switch knows nothing about trunking and subinterfaces in this mode.

You can't ping subinterface .2 because vlan2 is not configured on the switch. Same thing when pinging from the router.

If you were to configure an address on the physical interface, you would be able to ping to and from it as long as your laptop is in the same subnet.

If you dell switch doesn't support vlans and 802.1Q you may want to look into acquiring a cisco switch, preferably a 2950 or one in the 2900 series.

If anything I explained is unclear, feel free to ask for clarification.

Please be sure to let us know how it turns out.

iproute

rakem wrote:

but its a dell switch

markzab

rakem wrote:

but its a dell switch

BLASPHEMY!

Kaminsky

DELL make switches !!!!!!

They'll take over the world ya know !!!!! If we don't stop them soon!

EDIT: lol last 3 posts almost simultaneous

malcybood

Hey man,

The thing you need to ensure is that the switch port to the router is trunked. What model of switch do you have? Can you get a config of the switch? Is it a brand new switch with no config on it?

Here is the link to a Dell 3348 on how to configure inter-VLAN routing, but it is based on a Dell router not Cisco (same idea though). You should be able to piece it together from this....Ensure Step 7 in this document is configured on the switch. You have to trunk the port then also "allow" the VLANs

http://www.dell.com/downloads/global/products/pwcnt/en/app_note_38.pdf

Your router config is fine and the fact you have specified VLAN 1 on a subif does not matter in getting it to do what you want it to for the time being.....You can sort that out later once you know how to get it working. You will still be able to have connectivity despite it not being the "proper" way to configure the router.

I had VLAN 1 on a subif until I read something about that and changed it, but it did work OK, anyway that aint to do with your main problem.

Try the above info and see if you get anywhere and can get configs for the switch to post on the thread.

Malc

DirtySouth

tech-airman wrote:
DirtySouth,

According to Wendell Odom, CCIE #1624, in his book "CCNA Self-Study CCNA ICND Exam Certification Guide", page 309, Example 8-7 - Router Configuration for the 802.1Q Encapsulation Show in Figure 8-19 states:
interface fastethernet 0
ip address 10.1.1.1 255.255.255.0
!
interface fastethernet 0.2
ip address 10.1.2.1 255.255.255.0
encapsulation dot1q 2
!
interface fastethernet 0.3
ip address 10.1.3.1 255.255.255.0
encapsulation dot1q 3
Odom states after Example 8-7 that "The router IP address in the subnet of the 802.1Q native VLAN is configured on the physical interface instead of the subinterface...Also note that for the native VLAN, VLAN 1 in this case, the encapsulation command should not be used, or the router will encapuslate frames in an 802.1Q header."

So I'm going to follow what Odom says about assigning an IP address to the physical interface for 802.1Q trunk routing.

Source:
CCNA ICND Exam Certification Guide (CCNA Self-Study, 640-811, 640-801) - http://www.ciscopress.com/bookstore/product.asp?isbn=158720083X&rl=1

I never said that you couldn't assign an ip address to the interface, but there is no reason to do so. This is the way I've always done it and it works just fine.

There are plenty of examples either way on Cisco's site, so feel free to read up there as well.

contr04

dell switches use a liscensed version of CISCO IOS. of course they support trunking etc. only differences are default options on vtp etc.