cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
1081
Views
0
Helpful
4
Replies

Question about Intervlan routing on a catalyst 3750 switch

aboudhina
Level 1
Level 1

I have been looking into this for a while and I can't seem to figure out why my 2nd vlan is not able to connect properly to the net. I would be grateful if someone could take a look and advise on what Im doing wrong.

My switch has 12 ports where my devices connects directly, they are all on Vlan 1 and they all work perfectly.

on Port 12 I have a dlink router that is connected to a cable modem. the dlink router has an Ip address of 192.168.0.20

I created a second vlan (vlan2) and enabled dhcp relay on it. then I assigned port 9 on the switch to  (vlan2)

my laptop which is connected to port 9 seems to get an ip address fine and able to ping only some devices on my network (vlan1) and is not able to go out to the internet.  I think it has to do with the routes

vlan 1 is giving this default route :  0.0.0.0 0.0.0.0 192.168.0.20 192.168.0.52 10

vlan 2 is giving this one : 0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.51 10

why is my default routes look different for the 2 Vlans  (the underlined) ? any idea on why vlan1 works and not vlan2 ?

here is my switch's config :

!

! Last configuration change at 00:25:58 UTC Mon Dec 19 2011

! NVRAM config last updated at 00:19:57 UTC Mon Dec 19 2011

!

version 12.2

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname S3750

!

boot-start-marker

boot-end-marker

!

enable secret 5 $1$kGRQ$mNfjtNRp6moUunJOlRPX71

!

!

!

no aaa new-model

clock timezone UTC -5

switch 1 provision ws-c3750g-12s

system mtu routing 1500

ip routing

!

!

!

!

!

!

!

!

spanning-tree mode pvst

spanning-tree extend system-id

!

vlan internal allocation policy ascending

!

!

!

!

interface GigabitEthernet1/0/1

!

interface GigabitEthernet1/0/2

!

interface GigabitEthernet1/0/3

!

interface GigabitEthernet1/0/4

!

interface GigabitEthernet1/0/5

!

interface GigabitEthernet1/0/6

!

interface GigabitEthernet1/0/7

!

interface GigabitEthernet1/0/8

!

interface GigabitEthernet1/0/9

switchport access vlan 2

!

interface GigabitEthernet1/0/10

!

interface GigabitEthernet1/0/11

!

interface GigabitEthernet1/0/12

!

interface Vlan1

ip address 192.168.0.1 255.255.255.0

!

interface Vlan2

ip address 192.168.1.1 255.255.255.0

ip helper-address 192.168.0.3

!

ip default-gateway 192.168.0.20

ip classless

ip route 0.0.0.0 0.0.0.0 192.168.0.20

ip http server

ip http secure-server

!

!

ip sla enable reaction-alerts

!

snmp-server community public RO

snmp-server community private RW

snmp-server location Home

!

!

line con 0

password cisco

login

line vty 0 4

password cisco

login

line vty 5 15

login

!

end

Here is the routing table on Computer 1 ( on Vlan 1) :

===========================================================================
Interface List
12...1c 6f 65 c1 a3 d3 ......Realtek PCIe GBE Family Controller #2
11...1c 6f 65 c1 3c 72 ......Realtek PCIe GBE Family Controller
  1...........................Software Loopback Interface 1
15...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
14...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0     192.168.0.20     192.168.0.52     10
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
      192.168.0.0    255.255.255.0         On-link      192.168.0.52    266
     192.168.0.52  255.255.255.255         On-link      192.168.0.52    266
    192.168.0.255  255.255.255.255         On-link      192.168.0.52    266
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link      192.168.0.52    266
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link      192.168.0.52    266
===========================================================================
Persistent Routes:
  None

IPv6 Route Table
===========================================================================
Active Routes:
If Metric Network Destination      Gateway
  1    306 ::1/128                  On-link
11    266 fe80::/64                On-link
11    266 fe80::e98d:c724:7ef5:244a/128
                                    On-link
  1    306 ff00::/8                 On-link
11    266 ff00::/8                 On-link
===========================================================================
Persistent Routes:
  None

and here is the routes on the computer that is on Vlan 2 


===========================================================================
Interface List
15...f0 de f1 47 be 71 ......Intel(R) 82577LM Gigabit Network Connection
14...00 27 10 49 c8 b8 ......Intel(R) Centrino(R) Advanced-N 6200 AGN
  1...........................Software Loopback Interface 1
13...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
27...00 00 00 00 00 00 00 e0 Microsoft Teredo Tunneling Adapter
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      192.168.1.1     192.168.1.51     10
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
      192.168.1.0    255.255.255.0         On-link      192.168.1.51    266
     192.168.1.51  255.255.255.255         On-link      192.168.1.51    266
    192.168.1.255  255.255.255.255         On-link      192.168.1.51    266
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link      192.168.1.51    266
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link      192.168.1.51    266
===========================================================================
Persistent Routes:
  None

IPv6 Route Table
===========================================================================
Active Routes:
If Metric Network Destination      Gateway
  1    306 ::1/128                  On-link
  1    306 ff00::/8                 On-link
===========================================================================
Persistent Routes:
  None

thank you for your time

4 Replies 4

Hi,

Change the default gateway address to the IP address of the dlink router.

Regards,

Smitesh

you have ip routing enabled, so you don't need this L2 command line

ip default-gateway 192.168.0.20

type this:

no ip default-gateway 192.168.0.20

cadet alain
VIP Alumni
VIP Alumni

Hi,

1)You should put the DHCP server on your 3750:

eg

ip dhcp excluded-address 192.168.0.1

ip dhcp excluded-address 192.168.1.1

ip dhcp pool LAN1

network 192.168.0.0 255.255.255.0

default-router 192.168.0.1

dns-server 8.8.8.8

ip dhcp pool LAN2

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

dns-server 8.8.8.8

2)Make the port going to  the Dlink as a routed port:

int g1/0/12

no switchport

ip address 192.168.3.1 255.255.255.0

on the Dlink change the IP to 192.168.3.20

3) change your default route on 3750:

no ip route 0.0.0.0 0.0.0.0 192.168.0.20

ip route 0.0.0.0 0.0.0.0 192.168.3.20

4) remove the dhcp relay from the SVI:

    int vlan 2

    no ip helper-address 192.168.0.3

5) remove the DHCP service from the 192.168.0.3 interface

Regards.

Alain

Don't forget to rate helpful posts.

I was able to get it to work by adding a route on my dlink to recognize the secondart (Vlan 2) (subnet  192.168.1.0)

Im using 2 windows server boxes ( 2003 and 2008 ) running DHCP/DNS/AD/IIS/Exchange 2010 I'm perefer keeping things running on my windows boxes.

I also rather keep the routing between the 2 subnets happening on the L3 switch. the DLink is a cheap router (DIR655) that doesnt even support routing between LAN subnets, I had to hack the config to get that part to work.

thank you all for your suggestions.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Review Cisco Networking products for a $25 gift card