10-09-2010 01:11 PM - edited 03-06-2019 01:24 PM
hi all,
Here is info from pm pc
Ethernet adapter Local Area Connection 2:
Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 192.168.10.4
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.10.2
***************************************************************************************
My pc is connected to switch 2950 which has default gateway config as shown
ip default-gateway 192.168.10.1
Also it has trunk ports to switch A and B which are running HSRP on Vlan 10.
2950T# sh int trunk
Port Mode Encapsulation Status Native vlan
Fa0/8 desirable 802.1q trunking 1
Fa0/13 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Fa0/8 1-4094
Fa0/13 1-4094
Port Vlans allowed and active in management domain
Fa0/8 1,10,20,30
Fa0/13 1,10,20,30
Port Vlans in spanning tree forwarding state and not pruned
Fa0/8 none
Fa0/13 1,10,20,30
2950T# sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
3550SMIA Fas 0/8 121 R S I WS-C3550-2Fas 0/8
3550SMIB Fas 0/13 170 R S I WS-C3550-2Fas 0/13
2950T#
Switch A is HSRP Active and B is standby.
here is info
Switch A
3550SMIA#sh run int vlan 10
Building configuration...
Current configuration : 169 bytes
!
interface Vlan10
ip address 192.168.10.1 255.255.255.0 ***********************************************default gateway for vlan 10
standby 1 ip 192.168.10.3
standby 1 priority 150
standby 1 preempt
standby 1 track FastEthernet0/8 60
end
3550SMIA#sh standby
Vlan10 - Group 1
State is Active
14 state changes, last state change 00:32:01
Virtual IP address is 192.168.10.3
Active virtual MAC address is 0000.0c07.ac01
Local virtual MAC address is 0000.0c07.ac01 (v1 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 1.140 secs
Preemption enabled
Active router is local
Standby router is 192.168.10.2, priority 100 (expires in 9.280 sec)
Priority 150 (configured 150)
Track interface FastEthernet0/8 state Up decrement 60
IP redundancy name is "hsrp-Vl10-1" (default)
Switch B
3550SMIB#$ sh run int vlan 10
Building configuration...
Current configuration : 109 bytes
!
interface Vlan10
ip address 192.168.10.2 255.255.255.0
standby 1 ip 192.168.10.3
standby 1 preempt
end
My question here is even though my pc is connected to 2950 switch on port fa0/5 which is in vlan 10 and switch 2950 has default gateway of 192.168.10.1 that is vlan 10 ip of Switch A why my pc is showing default gateway of 192.168.10.2 that is vlan 10 ip of HSRP Switch B which is standby??
Many thanks
mahesh
Message was edited by: mahesh18
Solved! Go to Solution.
10-09-2010 01:48 PM
mahesh18 wrote:
also here is config from Switch B
!
ip dhcp pool Vlan10
import all
network 192.168.10.0 255.255.255.0
default-router 192.168.10.2 255.255.255.0
dns-server 64.59.135.145
Mahesh
As Christopher says, you are handing out the wrong default-gateway. Change -
default-router 192.168.10.2 255.255.255.0
to
default-router 192.168.10.3 255.255.255.0
Jon
10-09-2010 02:37 PM
Not only is it a best practice for the IP host default gateway to be the HSRP standby (virtual) address; but it's the only way it will work if there is a failure in a fault tolerant topology.
10-09-2010 01:22 PM
HSRP is a next-hop redundancy protocol and does not send an IP host default gateway information. There is an assumption that an IP host that's dependant on HSRP will be configured with the default gateway of the HSRP standby address.
How does your PC receive it's IP configuration information? Is it statically assigned or dynamically assigned?
If it's statically assigned then simply change the default gateway on the PC to 192.168.10.3.
If it's via DHCP you'll need to change the scope to issue a default gateway of 192.168.10.3.
Chris
10-09-2010 01:39 PM
Hi,
thanks for reply
pc gets ip dynamicall
mahesh
10-09-2010 01:45 PM
also here is config from Switch B
!
ip dhcp pool Vlan10
import all
network 192.168.10.0 255.255.255.0
default-router 192.168.10.2 255.255.255.0
dns-server 64.59.135.145
10-09-2010 01:48 PM
mahesh18 wrote:
also here is config from Switch B
!
ip dhcp pool Vlan10
import all
network 192.168.10.0 255.255.255.0
default-router 192.168.10.2 255.255.255.0
dns-server 64.59.135.145
Mahesh
As Christopher says, you are handing out the wrong default-gateway. Change -
default-router 192.168.10.2 255.255.255.0
to
default-router 192.168.10.3 255.255.255.0
Jon
10-09-2010 01:53 PM
Try this:
ip dhcp pool Vlan10
no default-router 192.168.10.2 255.255.255.0
default-router 192.168.10.3
exit
From a design perspective it's not such a great idea to have the DHCP server on a switch that's protected with HSRP as it's expected that when one of the redundant switches fails the other will take over seamlessly. Consider turning up a UNIX box as a DHCP server. Of course the UNIX box should have dual power supplies and dual NIC's.
Chris
10-09-2010 02:11 PM
Hi christopher,
this is for my home lab only.
you want me to try this on switch A or B ?
Many thanks
10-09-2010 02:30 PM
The default gateway should be the same.
Beware - If both switches are serving the same DHCP IP range you'll have DHCP conflicts.
You should divide the pool up between them so that they will not allocate the same IP address space. For instance; 192.168.10.0/25 on one switch and 192.168.10.128/25 on the other switch. In a lab you may not see a problem; but in production things things will get uncomfortable.
Chris
10-09-2010 02:33 PM
Hi Jon and christopher ,
Many thanks for the info
i change the default router on
Switch B
3550SMIB(config)#ip dhcp pool Vlan10
3550SMIB(dhcp-config)#df
3550SMIB(dhcp-config)#defa
3550SMIB(dhcp-config)#default-router 192.168.10.3
now my pc shows default gateway as 192.168.10.3 which is virtual IP.
so just to confirm point when we config the hsrp and we have dhcp also on switch then it is best practice to config the default router to virtual IP?
mahesh
10-09-2010 02:37 PM
Not only is it a best practice for the IP host default gateway to be the HSRP standby (virtual) address; but it's the only way it will work if there is a failure in a fault tolerant topology.
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