Solved: SAP Traffic Conditional flow - URGENT Help

nasr.khan · ‎10-16-2009

Hi, I have got a scenario with tight goals.

DC----------Link 1-------------WH

DC----------Link 2-------------WH

Two point to point links between DataCenter and Warehouse. Link-1 I want to send all SAP Application traffic from DC to WH and its return traffic. All Other Traffic goes via Link-2.

Incase if Link-1 goes down then all traffic including SAP Application traffic should pass on Link-2.

Link-1 comes up then all SAP application traffic passes through it.

Is this doable without any manual process

Giuseppe Larosa · ‎10-19-2009

Hello Nasr,

sorry for the disappointing tone I understand that you would like to verify what is suggested here.

yes, the thread has seen several developments and be aware that deploying QoS is still possible and recommended also with PBR as noted by Joseph in one of his last posts.

PBR as described in my post at time 10:17 is used to divert selected traffic flows over link2.

to be sure that all other traffic flows go on link1 is enough to make link1 more attractive for EIGRP routing protocol you use.

for this reason that final note saying that you still need to deploy EIGRP routing.

To do this you can use the bandwidth or delay commands in interface config mode only if link1 is not already preferred by EIGRP.

you can check this with

sh ip route for IP subnet in other side:

if you see a single IP route via link1 you are fine.

if you see two paths one via link1 and one via link2 of equal cost you need to manipulate BW or delay.

reduced BW or increased delay on link2 makes link1 preferred.

for PBR see

http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_ip_prot_indep_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1056703

also search netpro for other configurations of PBR on the archives

Hope to help

Giuseppe

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Joseph W. Doherty · ‎10-19-2009

BTW, if you're only using 12 to 35 K on a 5 Mbps link, and you're seeing drops, one might argue you should send all your traffic to the other link and stop paying for that "bad" link.

Also BTW, you might only be â€œusingâ€ 12 to 35 K because of a very poor quality link. Enough drops will tend to cause TCP flows to craw although perhaps without "breaking" the application.

Of course, many other things could be an issue too (or the root problem). You might want to reconsider Paolo's original suggestion and obtain some on-site consultation to review your situation.

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paolo bevilacqua · ‎10-16-2009

This is easily done with routing, but you need a qualified engineer to configure it - hire one for the job.

Please no dot solicit urgent help on a free volunteered forum - for professional help buy a service contract.

Joseph W. Doherty · ‎10-16-2009

"Is this doable without any manual process"

From what you've described, likely doable using PBR, although I would suggest consideration of utilization of QoS to guarantee performance of SAP on either link (then link dedication for SAP likely unnecessary - would also better handle failure mode if only one link was active too [e.g. failure of link-1]).

Giuseppe Larosa · ‎10-17-2009

Hello Nasr,

as suggested by Joseph if you deploy the correct QoS configuration to provide enough resources to SAP application you can simply use standard destination based load-balancing and you have fault-tolerance too.

Dedicating a link to SAP traffic using PBR may be good enough in normal scenario, but if one link fails you still need QoS to manage competition for link resources between different applications flows.

At the end it is better to deploy QoS on both links and to use them in load balancing.

Try to understand what the SAP applications traffic patterns are.

Hope to help

Giuseppe

paolo bevilacqua · ‎10-17-2009

In many case PBR is not even necessary.

Just inject an host route for the SAP server on a link only, and traffic will stick there. For the other routes set an higher metric.

Again, all things supposedly done easily by an engineer, while an end sure attempting alone will just struggle.

nasr.khan · ‎10-17-2009

Hi, Mr.Giuseppe

Thanks for replying. I would like to test with your advice.

Cisco Documentation is too widespread, can you help with config guidelines.

Thanks to p.bevilacqua for his reply too.

Giuseppe Larosa · ‎10-18-2009

Hello Nasr,

let's suppose your links are 100 Mbps and that your analysis of SAP needs says you should provide 35 Mbps for SAP.

the QoS tool to be used is a scheduler that is a queue manager.

Sw queues are created with one dedicated to SAP traffic.

class saptraffic

match access-group sap

police-map DCtoDC

class saptraffic

bandwidth 35000

class class-default

fair-queue

random-detect

int f0/0

service out DCtoDC

int f0/1

service out DCtoDC

this can be a possible QoS setup, SAP is guaranteed 35 Mbps of traffic when the link is full and can use more when the link is empty.

CBWFQ is elastic and allows reuse of unused resources: if no SAP traffic is running all other traffic can use all the link bandwidth.

the amount of bandwidth for SAP is the value when only one link is live to take in account this fault.

Note:

to be able to use this QoS tool you need a suitable HW platform and IOS version.

For example this can be done on a router or on a C6500 on flexwan, SIP, or ES linecards.

So this can apply to you or not.

Hope to help

Giuseppe

nasr.khan · ‎10-19-2009

Great Help Mr. Giuseppe.

At WH one link has packet drop issues and cannot be fixed soon.

Advice on this approach.

Link1 = 5MB ( Packet drops on link )

Link2 = 2MB ( Link is Ok )

If there are packet drops then SAP application will hang. So for now, need SAP traffic to pass over Link2 and other traffic (SMTP,directory replication,antivirus updates,backup) on Link1.

Planning to configure gre tunnel on each Link with EIGRP routing protocol.

Tricky part is how to send SAP traffic from Link2 and other traffic from Link1.

PBR can help, but not clear on config reqd.

Server range at DC 10.1.1.0/24

SAP Server configured with IP 10.1.1.25/24

WH IP range 10.7.4.0/23

Giuseppe Larosa · ‎10-19-2009

Hello Nasr,

I had supposed the two links have equal speed but this is not the case in your scenario.

I wouldn't add GRE tunnels to the picture they add their encapsulation overhead (24 bytes or more) and complexity to the solution.

PBR example

access-list 112 permit ip host 10.1.1.25 10.7.4.0 0.0.1.255

route-map divertSAP permit 10

match ip address 112

set interface link2

PBR has to be applied to the LAN interface(s) that receives traffic that has to go on the WAN links

let's suppose it is fas0/0

int fas0/0

ip policy route-map divertSAP

on the other side:

access-list 111 permit ip 10.7.4.0 0.0.1.255 host 10.1.1.25

route-map divertToSAP permit 10

match ip address 111

set interface link2

again has to be applied to lan interface

int f0/0

ip policy route-map divertToSAP

note: still deploy EIGRP routing over the two links

Hope to help

Giuseppe

Joseph W. Doherty · ‎10-19-2009

"If there are packet drops then SAP application will hang. So for now, need SAP traffic to pass over Link2 and other traffic (SMTP,directory replication,antivirus updates,backup) on Link1. "

BTW, if SAP traffic is being impacted by insufficient bandwidth due to bandwidth congestion due to other application traffic (as you seem to describe), then QoS, providing SAP traffic guaranteed bandwidth, should also relieve the problem.

nasr.khan · ‎10-19-2009

Thanks for taking interest in this post and replying.

Its not a bandwidth congestion issue but packet drop. Any active SAP session will hang if packet drops.

Idea is to start with reliable link for SAP and use the other link for replication/backup/updates... till its fixed.

if packet drop issue can be overcome with QOS then I am fine.

Joseph W. Doherty · ‎10-19-2009

Packet drops are usually a symptom of bandwidth congestion (even if transient).

nasr.khan · ‎10-19-2009

I do agree if link is on production and used. My scenario Link utilization is 12K to 35K only. Service Provider confirms issues on the link and needs time to fix. New link will take 2Month.

In my scenario its a WH (WareHouse) far from city with limited service provider options.

Can I get config guidelines on PBR to start with

paolo bevilacqua · ‎10-19-2009

User search box top right corner: "policy routing".

Giuseppe Larosa · ‎10-19-2009

Hello Nasr,

>> Can I get config guidelines on PBR to start with

may I ask you if you have read my previous post?

I've spent some minutes to provide you a possible solution

read the following:

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtpbrtrk.html

Hope to help

Giuseppe