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DNS problem with 7750

Occasional Advisor

DNS problem with 7750

i have configure 7750 with new VLAN to get DHCP from a new ADONIS box. the DHCP relay is work fine but my pc which in new VLAN cannot go to the internet. Currently the old DNS server using WIndows Server still working in the network.

my partial config:


 local-server nas-ip key 3com


 domain default enable system


 dhcp-server 1 ip ----old DNS server

 dhcp-server 2 ip ----this is new ADONIS box


vlan 50

 description Level5_VLAN_50

vlan 204

 description Level4_VLAN

interface Vlan-interface50

 ip address

 dhcp-server 2

 vrrp vrid 50 virtual-ip

 vrrp vrid 50 priority 110


interface Vlan-interface204

 ip address

 dhcp-server 1

 vrrp vrid 204 virtual-ip

 vrrp vrid 204 priority 90


1.currently old VLAN 204 using for DHCP relay and user can go to the internet.

2. new VLAN 50 using for DHCP relay  and user can get the IP address but can't go to the internet

3. i have try to use static IP using VLAN 204 and point to and can go to internet

4.i also try to use static IP using VLAN50 and point to DNSserver) and can't go to the internet

5. user from VLAN 204 can ping user in VLAN 50

6.VLAN 50 can ping adonis ( but adonis cannot ping VLAN 50


anyone have idea?




Super Advisor

Re: DNS problem with 7750

It seems that you have a misconfigured route back from your Adonis box to your network (VLAN 50) or vice versa. This makes any sense? Did you trace the route in both ways? The DHCP relay settings are correct in the switch; if there's some configuration problem this will be in the server, not in the switch. Perform a trace route in both ways and post it here.


Occasional Advisor

Re: DNS problem with 7750

seem i have settle that problem. actually i forgot to tell you guys that the situation isactually 2 unit of redundant 7750.

  1. i tried to trace from new vlan to internet and it stopped at firewall.

  2. i ping to adonis and success

  3. then i ping from adonis to new vlan interface,it turn time out

  4. so i assumed firewall has blocked the traffic from adonis to the new vlan

  5. i check the firewall and add new static route from adonis to new vlaninterface..but still face the same problem

  6. after i check firewall , proxy & i assume it must be something with the core switch.

  7. so i configure the 2nd core switch with the new vlan then my pc can go to the internet

is it we must configure the 2nd core switch with the same config to let new vlan user to go to the internet? but before configure the 2nd core switch..i can grab the IP address and DNS setting. whats your idea?