Utility of loopback on vlan interfaces

Hello,
Do you know where i can find information about the use of loopback with Vlan interfaces?
I'am working on 3550 switches...
Thanx

Hi Daniel,
well i already passed the command, and the config, references.
In fact i do use loopback as a VSI (e.g. loopback 0 1 etc.) and i am looking to learn more about its interaction/utility with vlan interfaces. (can it makes a non member vlan response to a ping?)
Thanks

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Loopback on vlan interfaces

Hi there,
do anyone know about the utility of the "loopback set" flag under the Vlan interface command. Could it help to keep a vlan in up/up state for example?
Thanx.

A vlan interface is indeed "virtual". Setting the loopback will have little effect.
A vlan interface will be up/up when there is at least one member port for the vlan with an active link. A single active trunk port will suffice as well to get the interface active.
Regards,
Leo

Could I use "vlan interface" as a tunnel source of DMVPN ?

I have a router R2811 with a 9 port FE Switch module(HWIC-D-9ESW).
Could I use vlan interface as a tunnel source when configuring DMVPN ?
The vlan ports is on the 9 port FE Switch module.
Because it's used now in production,I can't try it.

Hello.
I think there is no restriction on software routers like 2811.
PS: using loopback could be a better idea.

Netflow on 6509 in Native Mode from Vlan Interface

I'm trying to get a 6509-E, running Cisco IOS Software, s72033_rp Software (s72033_rp-IPSERVICES_WAN-M), Version 12.
2(33)SXI9, RELEASE SOFTWARE (fc2), to send netflow traffic from a vlan interface to a Solarwinds server.
The server is not seeing all the vlan traffic, but does see all the traffic on the layer 2 ports (not netflow).
I've seen that a command, ip flow ingress layer2-switched vlan, needs to be enabled, but the OS I have does not support that command.
Or could it be that MLS is not configured except for a couple commands:
mls netflow interface
mls cef error action reset
netflow setup:
Flow export v5 is enabled for main cache
Export source and destination details :
VRF ID : Default
    Source(1)       10.31.101.1 (Vlan52)
    Destination(1) 10.30.2.196 (2055)
Version 5 flow records
14927339 flows exported in 615072 udp datagrams
0 flows failed due to lack of export packet
0 export packets were sent up to process level
0 export packets were dropped due to no fib
0 export packets were dropped due to adjacency issues
0 export packets were dropped due to fragmentation failures
0 export packets were dropped due to encapsulation fixup failures
0 export packets were dropped enqueuing for the RP
0 export packets were dropped due to IPC rate limiting
0 export packets were dropped due to Card not being able to export
interface:
interface Vlan52
description AN.VDI.stu
ip address 10.31.101.1 255.255.255.0
ip helper-address 10.31.149.200
no ip redirects
ip flow ingress
ip flow egress
ip pim neighbor-filter 98
ip pim sparse-dense-mode
ip cgmp

Enabling MLS was the fix.
mls netflow interface
mls flow ip interface-full
mls nde sender version 5
mls cef error action reset

VLAN Interface Command

Ok, I thought I had the reason for the VLAN interface command down. I thought it was either used for switch management or routing between VLANS? However, now I realized that some communication wont work with out this command which doesnt make sense. If I have a VLAN, then the switch will only switch packets to ports on the same VLAN. The only way, communication would work between VLANS is if I either enabled routing between VLANs with the VLAN Interface command, connected the switch to another multi-layer switch that did do routing between VLANS, or connected the switch to a router which routed between the VLANs.
However, I just got this new 3550 switch in, configured the correct ports with the assigned VLANs, and the only way my cisco ip phone would work is if the VLAN Interface for my voice-ip VLAN was configured. The 3550 is connected to a 4507. Now, can someone tell my why this is? You shouldnt have to configure the VLAN Interface, right?(unless I wanted to route between VLANs, which could be done by the 4507)

Sounds to me like you either dont have the dot1q trunk interface between your 4506 and 3550 working properly, or your 3550 is running the enhanced image which allows routing.
It would be nice to see your config on both the 3550 and the 4500 to determine the reason. Just a stab at how it should be configured is that on your 4506, you have it running VTP server or transparent with the defined Data and Voice Vlan's. You have a port configured for trunking (which connects to the 3550). On your 3550, you have configured it as a vtp client or transparent and have verified that it has received (or if transparent VTP you have configured) the appropriate VLAN's. You than specified "interface VLAN #" or whatever number for switch management and configured the port that connects to the 4500 as a trunk. Your port connected to the port has the auxillary or voice vlan configured. If this is how your equipment is configured and it still does not work, than look for the line "ip routing" in your 3550 and negate it with "no ip routing".
If still no worky worky, post your config.
Cheers,

ACE - Query VLAN Interfaces Status

Hi,
I am wondering what the status of the query vlan interface means in the command 'show ft peer detail':
Query Vlan IF State : UP, Manual validation - please ping peer
I am pretty sure that I did not see this status when I configured query vlan last time. Current version is A2(2.3).
Unfortunately this status does not seem to be documented anywhere on CCO.
I appreciate any help!
Thanks,
Daniel

Hi Daniel,
The FT Query VLAN interface is an optional, yet very good, feature to be used when using redundant ACE modules or appliances. Without it, if the FT VLAN was to go down, the standby ACE will no longer receive FT heartbeats from the active ACE and therefore take the active role. However, if the active ACE is still running fine in the active role, then you don't want the standby ACE to take over as active because that will put them into an active/active scenario, which may lead to connectivity issues.
This is where the FT Query VLAN interface comes in. If the FT VLAN goes down, the standby ACE will notice this, but before taking the active role, it will ping it's peer IP address configured on the interface that is designated as the FT Query VLAN. If the ping is successful, then it will stay in the standby role, thereby saving you some headaches.
The status that you are seeing is the ACE's way of telling you that the interface is UP, but if you want to know if it can successfully ping the peer IP address, then you would have to manually ping the peer IP address from the CLI. The ACE does not periodically check the ping connectivity through any automatic mechanism. The automatic mechanism is only triggered by the FT VLAN going down.
Does this help?
Sean

WLC - 4402/4 - Vlan Interface Addressing

I currently have 7 WLCs with the same Vlan interfaces defined across all 7 controllers. Does anyone know the best practice for addressing these interfaces on each of the WLCs. I currently have each unique Vlan interface assigned with the same IP address across all 7 WLCs. This is working. Should I leave it this way or should I assign each controller with a different address for the Vlan interface?

The controllers, assuming you have it configured as such, act as dhcp relay agents. Presumably, if the router got the wrong mac address in its arp entry, the dhcp message would be lost.
Clients could have taken a while before getting a dhcp addr (race condition for router arp entry) and not been able to work if dhcp was required.
That said, I've seen the controllers work with the dhcp server set to 255.255.255.255 so the ip helper addresses on the routers would pick up the requests.

High VLAN Interface utilization (6500/sup720)

Can anyone tell me why a VLAN interface would show 100% utilization for a givin VLAN? This is a sup720 we're talking about.
I understand that the bandwidth of a virtual interface is 1Gig but I thought this was more related to routing metric.
Users were actually seeing performance issues until we changed how the servers on this particular interface were replicating. Once we did this the VLAN interface utilization went down and performance went up.
It doesn't make sense to me that the VLAN interface would limit the actual throughput of the various ports that are mapped to it. Throughput should be related to the switch module 61xx, 65xx, 67xx and how it interfaces to the backplan and the backplan speed itself.
Any insights would be helpful......

If the layer 3 SVI was showing 100% that means it had a lot of traffic that was being layer 3 processed switched instead of hardware switched . Normally most traffic is hardware switched within the ASICS and never even gets passed up to that layer . What would cause this I'm not sure .

VLAN interface on ME2600X

I'm trying to configure a VLan interface on my ME2600X (for inband management), but the switch won't accept the command.
What am I missing? I need a way to combine layer-2 services and a management vlan on the same dot1q trunk into the ME2600X.
Geir Jensen

Hello Geir,
You can use service instances e.g.:
interface GigabitEthernet0/3
switchport trunk allowed vlan none
switchport mode trunk
dampening
mtu 9100
load-interval 30
media-type rj45
service instance 5 ethernet
description Management VLAN
encapsulation dot1q 5
rewrite ingress tag pop 1 symmetric
bridge-domain 5 – this will pop up message:
Bridge-domain 5 created
VLAN 5 does not exist, creating vlan
interface Vlan5
description Management VLAN
ip address 10.0.0.1 255.255.255.0
ip access-group MNGT-ACL in
end
adam

VPLS with IP in the vlan interface

I have this config in a Cat6500:
l2 vfi XXX manual
vpn id XXX
neighbor 1.1.1.1
interface vlan XXX
ip addrr 2.2.2.2
xconnect vfi XXX
With this config I can't reach from 6500 other equipments on this vlan with vpls.
It is ok to setup an ip address in a VLAN interface even if the interface have VPLS "xconnect" configuration?

Hi Guys,
I would like to put my idea only but i do't know if it is correct or not.
but if we defice any ip address on the interface than this will help us to improve anything but will appear in the routing table of PE router and it could be a part of it's routing and MPLS which is not required.
secondly we are trying to emulate layer2 briedge accross the VPLS backbone not the Layer 3 switch domain. than it could be possible that you configure routing accross the backbone but there is no such kind of mechanism to enable routing.
please rate if it helps.
Kamlesh SHarma

2960 Plus VLAN Interface

Hi, i have a 2960 which i need to replace as it is now end of life, the replacement Cisco recommendes is the WS-C2960+24TC-L which is one of the new 260 Plus models, can you tell me if you can create a VLAN interface on this switch as it states that this is a layer 2 switch only??
Thanks

Yes, you can create VLAN interfaces.

FWSM vlan interface

Hello, quick question I hope someone can help with.
Is it possible for me to create 2 vlan interfaces on the 6500 and have them both in the same subnet?
For a specific customer requirement I would like to have a vlan interface on the 6500 as default gateway, sat in it's own vrf, and then route all traffic inbound and outbound to this vlan through the FWSM interface, preferably in the same subnet. I don't think this will be possible so just looking for confirmation either way.
As I will be running EIGRP between a pair of central 6500's and 2 remote offices it will make things much easier for me advertise the connected FWSM interfaces in to EIGRP for access in/out of all my VRF'd subnets. If I need another subnet for each VRF FWSM next hop then I'll have to reditribute a list of statics which I don't really want to do.
The reason I am not just using the FWSM as gateway is because I need to run HSRP across 3 different devices (another 6500 in a second suite), and failover FWSM will only give me 1 level of redundancy for those gateways.
Hope that makes sense, let me know if you have further questions.
Thanks

Thanks Marvin. You do understand the question, and it occurred to me after writing the above that I could just use a single FWSM inside interface and route in and out of each VRF via that 1 interface (All VRF's belong to a single customer, just required for segregation of internal traffic).
The third 6500 running HSRP will be located in a DC 100km away connected via dual 1Gb circuits (3ms latency), and has it's own default route to a pair of ASA 5520's. If both FWSM's go down then the gateway will go live in the second site and traffic will be switched over our SP qinq tunnel to that gateway. Relevant BGP bits (MED), etc. will also be in place for seemless failover and traffic flow to and from the /23 pi range peered with the same ISP in each location..
Thanks again.
Chris

Ipv6 Vlan Interface EUI-64 assignation problem

Hello, I have 2 routers 1800 series with switch modules incorporated connected with IPv6. Everything is working fine except for the problem that when I assign an IPv6 address to a Vlan (using the EUI-64 format to the switch ports), it assigns the SAME interface id (last 64 bits of the IPv6) of a fastEthernet port (FE 0/0), to the vlan, causing an error problem of duplicity:
" c..T, overlaps with another prefix "
Why does the EUI-64 assigns the MAC address of the FastEthernet ports instead of the ones in the switch modules?

Thanks for the reply, but I just solved the problem. The problem was with the command IPV6 ADDRESS AUTOCONFIGURATION. This command definitely brings up a lot of trouble with VLAN ipv6 address assignation.
After some testing I concluded that:
1- If one interface has the IPV6 ADDRESS AUTOCONFIGURATION mode on, the interface could end up with more than one ipv6 global interface address.
2- You cannot assign this mode to a vlan interface without getting into configuration problems.
3- If a FastEthernet Interface has this mode on(IPV& A. A.), the router does not let you assign a global unicast address to the vlan interface, and gives the following error message:
%IPV6-6-ADDRESS: 3FFE:C00:C18:F100:213:C4FF:FE44:4961/64 can not be configurex
4- For the VLAN`s Interface ID you have to manually assign the link local address with the command line
IPV6 ADDRESS FE80::1 (or any other unique link local address) LINK-LOCAL.
This is for Vlans that are in a switch module of the same router.
All this testing was for a Cisco router 1800 series with a switch module integrated in the router.
Could be that this command is used for other specific occasions which I am not aware of.
Regards,
Grupo GTD

Catalyst 2912 additional Vlan interface won't come out of "shutdown"

I've got an old 2912 and I'm currently converting this network over from using the dafault Vlan1 as the administrative Vlan. I've configured an additional Vlan interface but when I do a no shut on the interface it will not come up. Any idea what's going on? I haven't worked on a 2912 in years.
interface VLAN1
ip address 169.2.128.226 255.255.255.192
no ip directed-broadcast
no ip route-cache
interface VLAN299
description MGMT
ip address 10.227.95.136 255.255.255.128
no ip directed-broadcast
no ip route-cache
shutdown

OK, I'll answer my own question. I found the answer in some 2912 documentation. "Only one management vlan can be administratively active at a time".

ASA 5545-X SVI/Vlan Interface

I am looking to deploy ASA 5545-X with Layer 3 Vlan Interfaces, the device out of the box dosent let you create vlan interfaces. Is there any module available which enables to create Switch Virtual Interfaces.
I was looking at I/O 6 ports Gigabit Ethernet card, but wanted to make sure before ordering.
Many Thanks

Hi,
You are only able to configure Sub Interfaces for the Vlan ID on your ASA model.
You can only configure actual Vlan interfaces with ASASM and ASA5505 model. This relates to the fact that ASA5505 has a switch module while your model does not.
I have no expirience with the ASASM but I would imagine its similiar to the FWSM which also used Vlan interfaces as its a module in an actual larger switch/router platform.
You can check this limitation from the Command Reference also
interface vlan For the ASA 5505 and ASASM, to configure a VLAN interface and enter interface configuration mode, use the interface vlan command in global configuration mode. To remove a VLAN interface, use the no form of this command. interface vlan number no interface vlan number Syntax Description
number
Specifies a VLAN ID.
For the ASA 5505, use an ID between 1 and 4090. The VLAN interface ID is enabled by default on VLAN 1.
For the ASASM, use an ID between 2 to 1000 and from 1025 to 4094.
- Jouni

Utility of loopback on vlan interfaces

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