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Highlighted

Onplus with multiple VLAN

Hi,

i am trying to set the network agent N100 on a trunk port on a switch (2960) without success regarding dhcp???

The problem is that the agent is not getting any ip address from a dhcp pool from a Cisco 1841 router acting as DHCP server. The topology is like this:

Router---------------------------------------------------------------------Switch--------------------------------------------------------------------On100

         fa0/0

         fa0/0.10

         fa0/0.20

The router is on the stick with subinterfaces. Ports connecting the router and On100 on the switch are 802.1q trunk ports. I also made a simulation of this topology on the GNS3 and with wireshark i can see  that dhcp discover are comming inbound fa0/0 but when i type the command:

R#show ip dhcp server statistics there are no received dhcp discover packets???It's very strange.

Did any one have experience with multiple vlan topology?

Thanks

18 REPLIES 18
Highlighted
Enthusiast

Onplus with multiple VLAN

Hello Delo,

I am going here off of a few documents I will link at the bottom but I think I have a solution for you.

The network agent itself does not need a trunk port going to it.  From what I've gathered from documentation you connect it to one of the vlans, and make sure you have inter-vlan routing enabled (which you do judging from your router on a stick setup) and the network agent uses the router to get CDP from all the other vlans.

I looked through the Device Feature guide and the 1841 router should support discovery of additional devices if the 1841:

If the 1800 Series ISR has SSH access, and Level 15 credentials are

entered under Credentials > Login and Credentials > Enable in the Device

Information window on the portal, the device information collected be

displayed, and the device's ARP and CAM tables will be used to discover

additional devices.

Give that a try and let me know how it goes.

Documents I referenced:

Best Practices for OnPlus Device Discovery:

https://supportforums.cisco.com/docs/DOC-17579

Onplus portal user guide (mostly page 217)

http://www.cisco.com/en/US/docs/net_mgmt/other_net_mgmt/onplus/portal/user_guide/onplus_portal_user_guide_7820144.pdf

Christopher Ebert

Network Support Engineer - Cisco Small Business Support Center

Highlighted

Onplus with multiple VLAN

Thanks for the response,

i will try this method tomorrow but it'a very strange because on one side the information is that you dont need the trunk port and that by using a router arp table the onplus will create a topology and on  the other that you need a trunk port na that the on100 will automatically create subinterfaces for every vlan. I will report how it goes.

Highlighted
Contributor

Re: Onplus with multiple VLAN

Delo,
We're using multiple VLANs with OnPlus successfully. According to the documentation you can do so using one of two methods. One is to setup a switch port as a span port and plug the Mon port of the ON100 into that port to capture information using the old port monitoring method. The other is how your doing it using a trunk port. We are also using the trunking method.

Some considerations:
1) Double check your VLAN/Trunk configuration to ensure all VLANs are being broadcast down trunk ports.
2) Try attaching a pc to that VLAN and see if it gets an IP via DHCP to confirm it is working as well.



Sent from Cisco Technical Support iPhone App

Shawn Eftink CCNA/CCDA Please rate all helpful posts and mark correct answers to assist others searching for solutions in the community.
Highlighted

Re: Onplus with multiple VLAN

Thanks for the reply. Is it possible for you to attach just the port configuration and a dhcp server part of the config for me to see?

Thanks in advance.

Highlighted
Contributor

Re: Onplus with multiple VLAN

Delo,

Take a look at the document link below.  Beginning on page 3 contains a sample configuration.  I would recommend reading the entire document to get your arms around the VLAN discovery functionality.  I can appreciate that when reading some of the documentation it can be confusing and lead you to believe that it can discover additional networks using Layer 3 routing.  That said, the one thing to keep in consideration is that OnPlus/ON100, other than the Network Scanning functionality, will not traverse Layer 3 boundaries to do additional discovery/monitoring.  You can manually add devices that are only accessible via Layer 3 and select to do some monitoring on those devices however they must be added manually and it will not attempt to access those devices via SSH/Telnet or SNMP.  As such, it won't do functions like backing up configurations.

OnPlus autodiscovery will only use Layer 2 and that is why you would need the VLAN Trunking with DHCP in each VLAN or to SPAN a switch port.  With VLAN trunking the ON100 will have an IP in the other VLAN and be able to discover devices on that now "local LAN".  With port spanning, the ON100 would discover based on packets it receives.  It can appear a little confusing but as long as  you keep in mind that the ON100 won't discover over a Layer 3, that will help to clarify some of the confusion.

http://www.cisco.com/en/US/docs/net_mgmt/other_net_mgmt/onplus/application_notes/multivlan/onplus_on100_vlan_discovery_782079601.pdfhttp://www.cisco.com/en/US/docs/net_mgmt/other_net_mgmt/onplus/application_notes/multivlan/onplus_on100_vlan_discovery_782079601.pdf

Shawn Eftink CCNA/CCDA Please rate all helpful posts and mark correct answers to assist others searching for solutions in the community.
Highlighted

Re: Onplus with multiple VLAN

Sdeftink,

as far that example is pretty straight forward cause there is just the config part as to configure the trunk port on a switch which i already configured as static. The trunk is definitely allowing all vlan traffic but the onplus agent when configured on the trunk can get an ip address only from a vlan1 (default native vlan) with fa0/0.1 (dot1q 1) but when i change the subinterface fa0/0.10 with dot1q 10 and create dhcp pool for vlan 10 the dhcp server doesn't receive dhcp discover although i can see dhcp discover with wireshark on that trunk.???

Highlighted
Contributor

Re: Onplus with multiple VLAN

Delo,
Can you try doing it without sub interfaces? We're not using and sub interfaces and DHCP is being provided by a different device on the respective VLANs. There may be an issue with the sub interface/DHCP/Trunking combination your using.

Sent from Cisco Technical Support iPhone App

Shawn Eftink CCNA/CCDA Please rate all helpful posts and mark correct answers to assist others searching for solutions in the community.
Highlighted

Re: Onplus with multiple VLAN

Unfortunately we need the topology "router on the stick"  because we are using a small 1841 router with only 2 interfaces and we have more than 2 networks in our topology. Here is basically the issue:

When you connect On100 agent on a trunk port on a switch and the agent start sending dhcp discovery the switch receives it without 802.1q tag (because the agent is not a switch, it is an end device) and put that data in native vlan (so if you configure that trunk port with vlan 10 as native it will put it in vlan10). The switch will forward that dhcp discovery on all vlan10 ports and all trunk ports (if they permit vlan10)  except the one the dhcp discovery was received on. At the end if you have dhcp server for the vlan10 it will send the offer and the On100 agent will get the ip address from the dhcp vlan10 pool. After receiving the ip address it is impossible for the virtual subinterfaces on the On100 agent to get different ip addresses for different vlans because it will always send data untagged on the trunk  and therefore that data will be put always in the same natime vlan so i believe that you have to set the credentials on the portal on the layer3 device (in my case router 1841) and by using router 1841 arp table the agent will create a topology for all vlans.

Highlighted
Contributor

Re: Onplus with multiple VLAN

Delo,

I believe I understand what you're saying.  At this point, if you've entered the credentials for the 1841, which is listed as a supported device (https://supportforums.cisco.com/docs/DOC-17501), you've got the trunking setup correctly,  you have DHCP available in each VLAN, and you've restarted the ON100 to ensure it utilizes the new trunking configuration rather than the standard access port configuration, then in theory it should be working.  We may have to wait for one of the Cisco OnPlus team members to look into this and see if they can reproduce the issue on their end to determine if it's just a compatibility issue with the router on a stick configuration or if there is something else going on.  Sorry I can't be of more assistance on this.

Shawn Eftink CCNA/CCDA Please rate all helpful posts and mark correct answers to assist others searching for solutions in the community.
Highlighted

Re: Onplus with multiple VLAN

No problem sdeftink Thanks anyway

Tomorrow i am going to the customer site and i will try it with a trunk and credentials on 1841 router and i will report the results.

Highlighted
Enthusiast

Re: Onplus with multiple VLAN

Hi Delo,

Reading through this thread, I'm not sure I understand the issue you have now.

Is your concern that a topology for each VLAN isn't displayed? The topology is based on the logical topology and is not VLAN specific. The topology rendering is based on if Cisco supported devices are used and the credentials are provided. This gives access to ARP tables and CDP information for those devices.

To verify the ON100 has discovered each VLAN if you go to ON100 device information and look under the "Info" tab. Scroll down and you should see the VLANs discovered and leases if DHCP is available on those VLANs.

Please let me know if you have additional questions.

Thanks,

The OnPlus Team

Highlighted
Contributor

Re: Onplus with multiple VLAN

Nice Aqib!!  I learn something new every day.

Delo,

He's right.  I looked at one of mine where I have data and voice VLANs and it's showing the DHCP IP Addresses assigned from each as well as the VLAN numbers and the sub interfaces used on the ON100 itself.

Information I will now find useful going forward. 

Shawn Eftink CCNA/CCDA Please rate all helpful posts and mark correct answers to assist others searching for solutions in the community.
Highlighted

Re: Onplus with multiple VLAN

Hi,

i attached a On100 agent on a trunk port, configured credentials on the portal for the layer 3 device and created dhcp pools for different vlan and i can see all devices but the topology is not correct...i mean the agent is attached on a switch i but on the toplogy all devices are attached to a single parent device which is a router??? I enabled cdp on all switches and on 1841 router. Do i have to manually create a topology by attaching child devices to parents or this can be done automatically?

Highlighted
Enthusiast

Re: Onplus with multiple VLAN

Is the On100 connected to a port on the router? If so, try the switch that is next in the topology if it is a supported device.

Thanks,

The OnPlus Team