Routing between VLANs questions

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  nbeacham Users Awaiting Email Confirmation Posts: 23 ■□□□□□□□□□

  September 2011

  I see on the office switch you configured the IP address on interface Vlan 1 and Vlan 2, this is incorrect.
  Look up router on a stick, you need to configure your sub interfaces on the office router with 802.1Q encapsulation and also be sure to configure a switch trunk port with the same encapsulation.

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  pham0329 Member Posts: 556

  September 2011

  There's multiple ways to route traffic between VLANs, and your way is one of them, although it's not very practical. As you've found out, you need one interface on the router for each VLAN, and on a production network with lots of VLANs, that's not a viable solution.
  
  The other 2 ways to route between VLANs is as nbeacham said, use a router-on-a-stick configuration. In this situation, you setup a trunk between your switch, and the router. The switch tags the data going to the router, and the router retag the frame for the destination vlan and send it back out to the switch.
  
  Third way is to use a L3 switch, which is a lot simpler and more scalable, but is not covered in ICND2.

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  MrXpert Member Posts: 586 ■■■□□□□□□□

  September 2011

  Hey thanks for all your help! I got it working. The router on the stick method is much more scalable as you mentioned. I setup four VLANS and used the router to allocate IP addresses automatically using DHCP and i was really pleased with how it was able to know which IP to give out and without fuss.

  I'm an Xpert at nothing apart from remembering useless information that nobody else cares about.

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  MrXpert Member Posts: 586 ■■■□□□□□□□

  September 2011

  I'm back for an update and also some help please.Using PT.
  
  The small network I set up has a router (HQ-R1) connected to a switch (1STFL-SWITCH). There is also another switch(called GROUND-SWITCH) which is connected to 1STFL-SWITCH via a cross over cable. This is all in one building.I setup the 1STFL-SWITCH as the vtp server and the ground floor (i.e GROUND-SWITCH) as the client. All seems to be working fine there with all the vlans groups being sent across the trunk link. All i had to do then was ensure the interfaces on the GROUND-SWITCH were in the correct vlan IDs
  
  Within 1STFL-SWITCH are vlans ADMIN, SALES and TECH. The GROUND-SWITCH has vlans TECH and HR
  So basically this means physically there's tech staff on both floors of the office and they belong to the TECH vlan
  
  I tested pinging everything I could from sub interfaces to ip host on each vlan and it works fine.
  
  my ip addressing scheme is such
  
  SALES=VLAN 20
  TECH=VLAN 30
  HR= VLAN 40
  ADMIN=VLAN 50
  
  
  SALES ON 192.168.20.0 /24
  TECH ON 192.168.30.0/24
  HR ON 192.168.40.0 /24
  ADMIN ON 192.168.50.0/24
  
  My questions are what happens if the company has another building like on a campus lan style topology and they want to have inter vlan routing between there also? would I need to connect up the HQ-R1 (in the original building) to their new switch? or would they simply have a switch which was trunked to one of existing switches?
  
  What if in this new building they wanted a router as well. Would the routers need to have sub interfaces to each other?
  
  I hope i'm making sense

  network 29th sept VLANS, trunks.jpg 61.5K

  I'm an Xpert at nothing apart from remembering useless information that nobody else cares about.

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  advanex1 Member Posts: 365 ■■■■□□□□□□

  September 2011

  It sounds to me like you're getting more into the design of networks, which is a completely different certification. You could do it with the server switch being trunked to another switch across the campus, but you have to keep in mind - what kind of cable do you use, how far is the distance, is that a viable option, etc. etc...
  
  Depends on how you would want to connect the routers together as well. Do you want to use hub and spoke? Do you want to allow both routers to face and route to the internet?
  
  You're making sense, but it's not necessarily something you have to worry about for the certification. That's something you need to look up in design and understand the concepts behind it.

  Currently Reading: CISM: All-in-One
  New Blog: https://jpinit.com/blog

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  MrXpert Member Posts: 586 ■■■□□□□□□□

  September 2011

  thanks for your help.
  
  When I was setting up the VLAN management interface on the switches, I set these to 192.168.1.2 (1STFL-SWITCH)and 192.168.1.3(GROUND-SWITCH). I set the ip default gateway command on each switch to "192.168.1.1" which is the IP address of the fa0/0 interface of the router on a stick. Is that OK?
  Or should I also create further virtual management interfaces on these switches to reflect each vlan that exists? for example
  Vlan 20 = management interface of 192.168.20.9
  vlan 30 = management interface of 192.168.30.9
  
  at the moment with only one vlan management interface assigned per switch, all the nodes can ping these addresses and I can telnet from any host to any switch. It is working correctly as far as I can see but i just wanted if the method i have used seems right.
  
  1STFL-SWITCH CONFIG
  interface Vlan1
  description MANAGEMENT VLAN1
  ip address 192.168.1.2 255.255.255.0
  !
  ip default-gateway 192.168.1.1
  
  
  
  GROUND-SWITCH CONFIG
  interface Vlan1
  ip address 192.168.1.3 255.255.255.0
  !
  ip default-gateway 192.168.1.1
  
  
  HQ-R1 CONFIG
  !
  interface FastEthernet0/0
  ip address 192.168.1.1 255.255.255.0
  duplex auto
  speed auto
  !
  interface FastEthernet0/0.20
  description SUB INTERFACE TRUNK ON VLAN 20 IN 192.168.20.0/24 SUBNET
  encapsulation dot1Q 20
  ip address 192.168.20.1 255.255.255.0
  !
  interface FastEthernet0/0.30
  description SUB INTERFACE TRUNK ON VLAN 30 IN 192.168.30.0/24 SUBNET
  encapsulation dot1Q 30
  ip address 192.168.30.1 255.255.255.0
  !
  interface FastEthernet0/0.40
  description SUB INTERFACE TRUNK ON VLAN 40 IN 192.168.40.0/24 SUBNET
  encapsulation dot1Q 40
  ip address 192.168.40.1 255.255.255.0
  !
  interface FastEthernet0/0.50
  description SUB INTERFACE ON VLAN 50 ADMIN ON 192.168.50.0/24 SUBNET
  encapsulation dot1Q 50
  ip address 192.168.50.1 255.255.255.0
  !
  interface FastEthernet0/1
  no ip address
  duplex auto
  speed auto
  shutdown
  !
  interface Serial0/3/0
  no ip address
  shutdown
  !
  interface Serial0/3/1
  description WAN
  ip address 172.16.0.2 255.255.0.0
  encapsulation ppp
  ppp authentication chap

  I'm an Xpert at nothing apart from remembering useless information that nobody else cares about.

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  pham0329 Member Posts: 556

  September 2011

  advanex1 wrote: »

  You're making sense, but it's not necessarily something you have to worry about for the certification. That's something you need to look up in design and understand the concepts behind it.

  
  That's something that he needs to worry about for the real world!

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  advanex1 Member Posts: 365 ■■■■□□□□□□

  September 2011

  pham0329 wrote: »

  That's something that he needs to worry about for the real world!

  
  Pham, I agree.
  
  MrXpert - yes, it looks fine. sometimes I throw the f0/0.1 subinterface and run the encapsulation dot1q from that, depends on how I feel for the day. I like working with subinterfaces rather than the physical for the native vlan. The management IP's on your switches look fine though.
  
  Forgot to say that since you are already using ROAS and the fact that you are routing between vlans, that gives you the option of keeping your management interfaces on the same network/subnet as the f0/0 interface on your router. To me, it's easier to track this way. Any PC should be able to telnet into your management interfaces if your intervlan routing is configured correctly.

  Currently Reading: CISM: All-in-One
  New Blog: https://jpinit.com/blog

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  pham0329 Member Posts: 556

  September 2011

  My questions are what happens if the company has another building like on a campus lan style topology and they want to have inter vlan routing between there also? would I need to connect up the HQ-R1 (in the original building) to their new switch? or would they simply have a switch which was trunked to one of existing switches?
  
  What if in this new building they wanted a router as well. Would the routers need to have sub interfaces to each other?

  
  If you have another building, you're probably going to want to use a L3 switch, rather than a ROAS. From there, you can either trunk the connection between the two L3 switches, or you would route between them using routing protocols. The advantage of routing between them is that broadcast from one building, is confined to that building, and doesn't traverse the link into the other building. If you have redundant switches, routing between them would mean that you're using routing protocols for convergence, rather than STP.

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