03-03-2011 10:16 AM
My first question, can anyone recommend some very heavy reading discussing the ACE modules and associated traffic flows and order of operations? Not just how-to scenarios.
And the primary question that brings me here:
I've got an ACE module in a 6500 chassis that's configured for routed mode. For the purpose of this question we'll say that on the ACE I have a single VLAN for vIPs and a single VLAN for rservers. vIP VLAN is 12 and rserver VLAN is 101. I have a pair of App servers being load balanced, and a pair of Web servers being load balanced.
When user devices send traffic to the Web servers vIP, traffic hits the SVI for VLAN 12 and the service-policy is applied manipulating that traffic and sending it to the VLAN 101 SVI and on down to an rserver. The same if user devices are sending traffic to the App servers vIP.
When a Web server tries to send over to the App servers vIP, I get no response. In fact, from the Web server I can't even ping my gateway (SVI for VLAN 101). How do I get the Web server to send traffic loadbalanced across the App servers?
Here's an example ACE config:
!
access-list ALL line 8 extended permit ip any any
!
probe tcp 5555
port 5555
interval 5
passdetect interval 30
!
probe http HTTP
interval 5
passdetect interval 30
expect status 200 200
!
rserver host APP01
description App Server 1
ip address 10.10.101.15
probe 5555
inservice
rserver host APP02
description App Server 2
ip address 10.10.101.16
probe 5555
inservice
rserver host WEB01
description Web Server 1
ip address 10.10.101.17
probe HTTP
inservice
rserver host WEB02
description Web Server 2
ip address 10.10.101.18
probe HTTP
inservice
!
serverfarm host APP-SERVERS
predictor leastconns
rserver APP01
inservice
rserver APP02
inservice
serverfarm host WEB-SERVERS
predictor leastconns
rserver WEB01
inservice
rserver WEB02
inservice
!
sticky ip-netmask 255.255.255.255 address both WEB-STICKY
replicate sticky
serverfarm WEB-SERVERS
sticky ip-netmask 255.255.255.255 address both APP-STICKY
replicate sticky
serverfarm APP-SERVERS
!
class-map match-any APP-VIP
description App Servers VIP
2 match virtual-address 10.10.12.21 tcp eq 5555
class-map match-any WEB-VIP
description Web Servers VIP
2 match virtual-address 10.10.12.20 tcp eq https
3 match virtual-address 10.10.12.20 tcp eq www
!
policy-map type loadbalance first-match L7-APP-SERVERS
class class-default
sticky-serverfarm APP-STICKY
policy-map type loadbalance first-match L7-WEB-SERVERS
class class-default
sticky-serverfarm WEB-STICKY
!
policy-map multi-match L4-CONTEXT-A-VLAN
class WEB-VIP
loadbalance vip inservice
loadbalance policy L7-WEB-SERVERS
loadbalance vip icmp-reply
class APP-VIP
loadbalance vip inservice
loadbalance policy L7-APP-SERVERS
loadbalance vip icmp-reply
!
interface vlan 12
description ACE-CONTEXT-A-vIPs
ip address 10.10.12.5 255.255.252.0
alias 10.10.12.4 255.255.252.0
peer ip address 10.10.12.6 255.255.252.0
access-group input ALL
service-policy input MGMT-ACCESS
service-policy input L4-CONTEXT-A-VLAN
no shutdown
!
interface vlan 101
description ACE-CONTEXT-A-SERVERS
ip address 10.10.101.2 255.255.255.0
alias 10.10.101.1 255.255.255.0
peer ip address 10.10.101.3 255.255.255.0
access-group input ALL
no shutdown
Solved! Go to Solution.
03-03-2011 12:13 PM
Hi Adam,
You can check Gilles' DC t-shooting guides that should give you a very good overwiew about packet processing on the ACE; also you can check
the Cisco wiki site where you find the scenarios plus a detailed explanation for traffic management.
Now going back to your issue, you problem can be splitted in two parts.
1. Web server not able to ping VLAN 101 ACE's SVI.
ACE is a closed device, meaning that access to each Interface/VLAN needs to be explicitly configured; you need to apply the management policy
to the 101 SVI to allow ICMP or any other management protocol. You can apply the same (service-policy input MGMT-ACCESS) or create a new
one just for ICMP, that's up to you.
2. Web servers not able to communicate with APP servers thorugh VIP.(vise-versa)
Problem here is that servers are trying to communicate through SVI 101 but no VIPs are applied to it so the ACE will simply discard the packets
for 10.10.12.20/10.10.12.21 on that interface, servers have the ARP and everything to reach those VIPs but the ACE has not been instructed to do
load balancing for clients reaching it out through VLAN 101.
In order to do load balancing between APP & Web Servers you need to configure L4-CONTEXT-A-VLAN on SVI 101 as well.
Also since your servers are sitting all in the same VLAN you're going to need client NAT to prevent assymetric routing on server-to-server communications.
I've attached a sample with NAT based on your config.
HTH
__ __
Pablo
03-03-2011 12:13 PM
Hi Adam,
You can check Gilles' DC t-shooting guides that should give you a very good overwiew about packet processing on the ACE; also you can check
the Cisco wiki site where you find the scenarios plus a detailed explanation for traffic management.
Now going back to your issue, you problem can be splitted in two parts.
1. Web server not able to ping VLAN 101 ACE's SVI.
ACE is a closed device, meaning that access to each Interface/VLAN needs to be explicitly configured; you need to apply the management policy
to the 101 SVI to allow ICMP or any other management protocol. You can apply the same (service-policy input MGMT-ACCESS) or create a new
one just for ICMP, that's up to you.
2. Web servers not able to communicate with APP servers thorugh VIP.(vise-versa)
Problem here is that servers are trying to communicate through SVI 101 but no VIPs are applied to it so the ACE will simply discard the packets
for 10.10.12.20/10.10.12.21 on that interface, servers have the ARP and everything to reach those VIPs but the ACE has not been instructed to do
load balancing for clients reaching it out through VLAN 101.
In order to do load balancing between APP & Web Servers you need to configure L4-CONTEXT-A-VLAN on SVI 101 as well.
Also since your servers are sitting all in the same VLAN you're going to need client NAT to prevent assymetric routing on server-to-server communications.
I've attached a sample with NAT based on your config.
HTH
__ __
Pablo
03-03-2011 12:55 PM
Pablo,
Makes sense to me. I appreciate your help! Oh, but where do I find "Gilles' DC t-shooting guides"?
03-03-2011 03:31 PM
Adam,
Don't mention it
You can find the guides on the application networking forum blog:
https://supportforums.cisco.com/community/netpro/data-center/application-network?view=blog.
Cya
__ __
Pablo
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