10-10-2008 09:21 AM
I have an issue with access to a VIP on the CSS. The CSS is designed as a Dual Arm with two interface bridging a L2 L/B Vlan and a L2 Non L/B Vlan. The firewall in front of the CSS acts as a L3 gateway.
Client > FW (L3 VLAN) > L2 Switch (L2) > CSS > L/B Server
I can get to the real server IP and port combination fine but hitting the VIP I see the flow created on the CSS and the return flow is sent but the firewall in front of the CSS never sees the SYN/ACK packet from the server.
Here are the flows for traffic :
sh flows 192.168.4.6
--------------- ----- --------------- ----- --------------- --- ------- ------
Src Address SPort Dst Address DPort NAT Dst Address Prt InPort OutPort
--------------- ----- --------------- ----- --------------- --- ------- ------
192.168.4.6 18397 10.65.16.40 8080 10.65.16.62 TCP e1 e2
sh flows 10.65.16.62
--------------- ----- --------------- ----- --------------- --- ------- ------
Src Address SPort Dst Address DPort NAT Dst Address Prt InPort OutPort
--------------- ----- --------------- ----- --------------- --- ------- ------
10.65.16.62 8080 192.168.4.6 18397 192.168.4.6 TCP e2 e1
I sniffed the traffic on the server and it replis to the original SYN packet and there's only one interface of that server.
What is strange is that I can get to the VIP successfully from the servers that are bridged to the CSS, like the non-load balanced servers in the same L3 VLAN. So traffic that does not need to pass through the firewall seems to work fine.
Sounds like a symetrical routing issues but I can't find the problem.
Any help would be greately appreciated.
Thank you.
Dmitry.
10-13-2008 10:51 AM
Correction to the above, the flow should be :
Client > FW (L3 VLAN) > L2 Switch (L2) > CSS > L2 Switch (L2) > L/B Server
Dmitry.
10-13-2008 11:03 AM
What is the default gateway on the server?
Is it the Circuit IP on CSS?
Is there any possibility that the response from the server is bypassing CSS?
Syed
10-13-2008 11:10 AM
Hi Syed.
The Server's default gateway is the FW L2 interface. (10.65.16.1 configured on the FW)
The Circuit IP address of the CSS is different - 10.65.16.8.
I do not think the server's reply is bypassing the CSS as I see the following flow
on the CSS from the server destined to the client :
sh flows 10.65.16.62
--------------- ----- --------------- ----- --------------- --- ------- ------
Src Address SPort Dst Address DPort NAT Dst Address Prt InPort OutPort
--------------- ----- --------------- ----- --------------- --- ------- ------
10.65.16.62 8080 192.168.4.6 18397 192.168.4.6 TCP e2 e1
dmitry.
10-14-2008 09:37 AM
These are the configurations on the L2 Switch:
New L/B L2 VLAN:
vlan 411
name Prod_Load_Balanced
Existing vlan:
vlan 111
name Prod_Non_Load_Balanced
I bridge the VLAN's to the CSS:
interface FastEthernet4/1
switchport access vlan 111
switchport mode access
speed 100
duplex full
no snmp trap link-status
interface FastEthernet4/2
switchport access vlan 411
switchport mode access
speed 100
duplex full
no snmp trap link-status
These are the interface and circuit configs on the CSS:
interface e1
phy 100Mbits-FD
redundancy-phy
description "Non-Load Balanced"
bridge vlan 111
interface e2
phy 100Mbits-FD
redundancy-phy
description "Load Balanced"
bridge vlan 111
circuit VLAN111
redundancy
ip address 10.65.16.8 255.255.255.0
Here is the service and content config from the CSS:
service apefl03d
protocol tcp
ip address 10.65.16.62
keepalive port 8080
port 8080
keepalive type script ap-kal-tcp-ports "10.65.16.62 8080"
keepalive frequency 30
active
owner APP
content Production
add service apefl03d
protocol tcp
port 8080
vip address 10.65.16.40
active
The Server's default gateway is the FW interface, 10.65.16.1.
dmitry.
10-30-2008 01:19 PM
This issue has been resolved. The firewall has two "inside" interfaces and the CSS was using the wrong MAC address (the second FW interface) to send the reply traffic.
I had to remove the "ip uncond-bridging" command and re-apply it to get the traffic to flow properly and also had to set up static routes to point to the default gateway of the FW for the particular subnet.
My understanding was that "ip uncond-bridging" command takes care of bridging and the CSS does not need to use the routing table. But if I remove the static routes traffic does not flow properly, it is being sent to the second FW "inside" interface but traffic comes in on the first "inside" interface and thus the FW silently drops it.
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