IOS SLB dns probe

Hi,
I'm trying to configure a DNS probe using IOS SLB, but it's not working.
I followed the manual on how to configure a DNS probe, but it just doesn't make any sense.
When using DNS probes on an ACE, you give a hostname which the DNS server should resolve to a configured IP Address.and configure an ip address, which makes sense.
On the IOS SLB, it is not the case. Two variables can be configured:
Router(config-slb-probe)# address ip-address]
(Optional) Configures an IP address to which to send the Domain Name System (DNS) probe.
Router(config-slb-probe)# lookup [ip-address]
(Optional) Configures an IP address of a real server that a Domain Name System (DNS) server should supply in response to a domain name resolve request.
What am I missing. Could someone please clearify??
Tnx!

To verify that a probe is configured correctly, use the show ip slb probe command:
Router# show ip slb probe
It may help you in troubleshooting purpose
For the further description for configuration for the DNS Probe following guide may help you
http://www.cisco.com/en/US/docs/ios/12_2/12_2z/12_2za/feature/guide/slbza5.html#wp2434837

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IOS SLB HTTP Probe

Hi, I have a simple SLB setup with two servers running in directed mode and two 6509's running IOS SLB to balance between the two. The two servers are web servers and require authentication when hit so I am just testing using a http probe and searching for the 401 code. Is there any gotcha's with configuring the credentials on the 6509 to log onto the webpage? Cheers, Brian

Can you post the following:
1. debug ip slb probe
2. debug ip slb probe conn
3. debug rtr error
4. debug rtr trace

IOS SLB and probe failure

Hello,
we use server-load-balancing with IOS 12.1(19)E1
We have a problem if the server receives more connections following error messages REAL 192.168.197.8 (HSSAT1-LX) has changed to PROBE_FAILED and few seconds later REAL 192.168.197.8 (HSSAT1-LX) has changed to OPERATIONAL appears and so on.
We checked the server and they works proper.
What could be the reason for probe failed?
My configuration:
ip slb probe HS-PROBE tcp
interval 5
ip slb serverfarm HSSAT1-LX
nat server
predictor leastconns
failaction purge
probe HS-PROBE
real 192.168.197.8 99
reassign 2
inservice
real 192.168.197.9 99
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ip slb vserver HS.SAT1.DE
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Is it better to use another probe (icmp)? or without any probe?
When does it make sense to use probes?
Best regards
Stefan

HI Stefan,
tcp probes do a complete TCP 3-way handshake and normaly terminate the session. A problem which I had some times timeout for a session to be established might be to short if the server is "heavy" loaded.
Probing on a specific method (TCP HTTP ...) is most of the times the better solution. Imagine a WEB-Server which is properly pingable but the httpd died due to some internal error. If you would probe on a per ping basis the loadbalancer will never notice this but if you monitor tcp-port 80 by a tcp probe or better a http probe you will notice this and the server would be taken out of the serverfarm. Even better but afaik not possible in IOS SLB is to probe a certain page e.g. index.html. As you know that the httpd is up and running and pages can be displayed.
Regarding the probing issue it might be usefull to read the follwing link describing healthmonitoring with the CSM
http://www.cisco.com/en/US/products/hw/switches/ps708/products_installation_and_configuration_guide_chapter09186a00801c5899.html#1024967
Hope that helped.
Best Regards,
Joerg

IOS SLB and DNS failover

Hi, there:
Is that possible I could use IOS SLB and DNS failover automatically?
i.e:
vip 10.1.1.1
vip 10.2.1.1
dns records:
vip1 10.1.1.1 10.2.1.1
normal condition:
vip1 will be 10.1.1.1
when 10.1.1.1 failed it will give 10.2.1.1
Is that something it could be done on IOS SLB, or other devices?
real services are udp based.gtp service
Thanks,

Yes, IOS server load balancing and the DNS failover can be done automatically. Is this not working currently? Can you posts the configuration so that we can check where the problem is.

IOS slb questions

Hi,
1. It is true that ip slb probe http is not working on 6509 without CSM card?
2. Did someone had tested how many IOS SLB client connections can support a 6509 with SUP1A /MSFC2 without CSM card?
Thanks,
Yuti

The Cisco CSM accommodates a wide range of common IP protocols?including TCP and User Datagram Protocol (UDP). Additionally, the Cisco CSM supports higher-level protocols, including HTTP, FTP, Telnet, Real Time Streaming Protocol (RTSP), Domain Name System (DNS), and Simple Mail Transfer Protocol (SMTP).
The Cisco CSM allows full regular expression pattern matching for policies based on URLs, cookies, and HTTP header fields. The Cisco CSM supports any URL or cookie format?allowing it to load balance existing Web content without requiring URL or cookie format changes.

IOS SLB versus CSM

Hi,
trying to figure out a possible solution for a 6500 and got a bit confused. According to my knowledge, IOS SLB is working either in L2 (MAC) or L3/4 (NAT), to ensure load balancing. CSM comes in the game, but offers much more, extending to L4/7. Are the two solutions substitude or complementary? Is it true that only with an CSM can you get HTTP probes to check your load balanced server farm? What other differences do you know about these two solutions?
In the paper http://www.cisco.com/en/US/partner/products/hw/modules/ps2706/products_configuration_example09186a0080094066.shtml
it is stated that "To run Cisco IOS SLB software, you must configure the mode using the show ip slb mode [csm | rp] command before any configuration. In the show ip slb mode command, the rp argument is default. You can only configure csm argument if you have the Content Switching Module (CSM)."
While in
http://www.cisco.com/en/US/partner/products/hw/modules/ps2706/products_configuration_example09186a008009452d.shtml
cisco states that "You cannot run Cisco IOS® SLB software on the same switch as the CSM."
Any ideas on that?
Thanks in advance

there are 2 ways to configure the csm.
You can use the same ios slb command and just tell the switch that there is a csm with the command 'ip slb mode'.
Or you can use the 'module contentswitching ' command.
If you use the first method, you can't use both a CSM and ios slb on the same switch.
If you use the second method, it is ok to have both ios slb and csm.
IOS SLB offers L4-7 loadbalancing solution.
Just be aware that as soon as you do L7 or do some nating, you poor performance with ios slb compare to a CSM.
One advantage of ios slb is the capacity to do radius loadbalancing [inspecting radius packet to identify framed ip, ...]
This is why in CMX solution we combine both ios slb and csm.
IOS SLB is used to loadbalance radius and the CSM is used to loadbalance the rest of the traffic.
Personally, I would say if you just need some vpn or firewall loadbalancing, ios slb is enough.
If you need HTTP or any other traffic wthe CSM is a better choice.
Regards,
Gilles.

IOS SLB RADIUS loadbalancing

Hi Guys,
can anyone confirm or point out errors in this config that I wish to pop on our 6509. We don't have a test environment, so I need to get as much feedback as I can on this.
Thanks in advance,
James
no natpool WSB_RADIUS 10.176.57.115 10.176.57.115 netmask 255.255.255.128
no serverfarm WSB_RADIUS
no serverfarm WSB_RADIUS_NAT
no policy WSB_RADIUS_NAT
no vserver WSB_RADIUS
no probe WSB_RADIUS_AUTH udp
ip slb serverfarm WSB_RADIUS
nat server
real 10.176.57.38
faildetect numconns 8 numclients 1
inservice
real 10.176.57.39
faildetect numconns 8 numclients 1
inservice
real 10.176.57.40
faildetect numconns 8 numclients 1
inservice
real 10.176.57.41
faildetect numconns 8 numclients 1
inservice
ip slb vserver WSB_RADIUS
virtual 10.176.57.115 udp 1813 service radius
serverfarm WSB_RADIUS
idle radius request 2
inservice standby WSB
interface Vlan130
standby 130 name WSB

IOS SLB provides RADIUS load-balancing capabilities for RADIUS servers. In addition, IOS SLB can load-balance devices that proxy the RADIUS Authorization and Accounting flows in both traditional and mobile wireless networks, if desired. IOS SLB does this by correlating data flows to the same proxy that processed the RADIUS for that subscriber flow.
http://www.cisco.com/en/US/products/sw/iosswrel/ps1833/products_feature_guide09186a00802081ce.html#wp2889077

IOS SLB and FWSM

Hi, this may be a silly question but is there any problem with configuring IOS SLB on a 6509 which also has a FWSM module in it and the Servers being load balanced are behind the FWSM?

The only thing to consider is that by FWSM, you most likely will be running multiple VRFs on the switch and IOS-SLB has some limitations regarding VRF.
IOS-SLB probes are sent to the global routing table (VRF default) and you will need to 'no advertise' and add static routes to null0 to the VRF for the virtual IPs.
Other than that, IOS-SLB works fine with the FWSM and VRF...

IOS SLB

Hi
I have configured IOS SLB vserver and serverfarm. There is a list of allowed clients.
But from two clients (with IP 10.171.4.*) there is Reset of connections. Other clients works OK.
ip slb serverfarm SF1
probe SF8888
real 10.91.14.90
weight 1
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retry 20
inservice
real 10.91.14.91
weight 1
faildetect numconns 4
retry 20
inservice
ip slb vserver VS1
virtual 10.91.14.19 tcp 8888
serverfarm SF1
idle 120
delay 5
client 10.91.14.32 255.255.255.255
client 10.91.14.38 255.255.255.255
client 10.91.14.41 255.255.255.255
client 10.91.15.30 255.255.255.255
client 10.91.15.31 255.255.255.255
client 10.171.4.64 255.255.255.255
client 10.171.4.65 255.255.255.255
inservice standby WA-SLB-1
Peter

Howdy,
You might want to post this in the application networking area :-)
Cheers
Andrew

IOS SLB Loab Balance Questions

Forgive me if this is the wrong forum but it was the closest one I found relating to my issue.
I've trying to load balance four of our radius servers using IOS SLB. The config works well and the radius servers are accepting requests fine. I follow this article which wasn't too bad to follow:
http://www.cisco.com/application/pdf/en/us/guest/netsol/ns377/c649/cdccont_0900aecd800eb95f.pdf
My two questions are:
1. Sticky Option
I understand it's used to make sure the client's accounting information
goes to the correct real server, but I'm not sure how it really works
and what's the best time to set it to.
Eg:
ip slb vserver RAD-UDP-1646
virtual 210.x.x.224 udp 1646
serverfarm RADFARM
sticky 86400 group 10
inservice
a/ The documentation says "This configuraion causes the sticky database to store its entries for 86,400 seconds of inactivity". What do they mean by "inactivity" - no radius packets coming through? inactivity from the user's end?
b/ It also says "the client's IP address is added to the IOS SLB database..." - is this the client's framed IP that the ISP assigns to the customer???
c/ And what would be the optimum time to set the sticky timer to be?
2. SLB connection statistics
core1-router#sh ip slb reals
real farm name weight state conns
203.x.x.74 RADFARM 8 OPERATIONAL 0
203.x.x.78 RADFARM 8 OPERATIONAL 0
203.x.x.79 RADFARM 8 OPERATIONAL 0
203.x.x.80 RADFARM 8 OPERATIONAL 2
When you disconnect, the slb stats still show you as being connected to
the real server (and both udp ports) which isn't very accurate. There is a default "delay" time which handles TCP disconnections and after being disconnected for 10 sec, the SLB stats are updated to reflect this (I've verified this works)- but nothing about how it handles UDP disconnections??? This
would skew the stats and give us a very bad misrepresentation of the
number of current and valid connections. Is there anyway to correct this???
Thanks.
Andy

Inactivity for IOS SLB means that after specified time of inactivity, the client will be free to be load balanced to another server. As long as they remain active without an idle time , they will remain connected to the same real server. For the client's IP address which is added to the IOS SLB database I think it is the frammed IP address which the ISP assigns. The optimum time for the sticky timer will be its default value or say 60 seconds.

IOS SLB and IBM Workload Manager

Does anyone know if IOS SLB can function similar to Multinode Load Balancing (MNLB) in that the IOS router acts as a Services Manager which contacts the OS390 Worload Manager (WLM) who then reports back the best OS390 server for a particular connection.
Under MNLB, the Local Director performs the task as the Services Manager, but can a IOS SLB router perform this task?
Thank you for your help.

Steve, thank you for the reply. I have a large-scale OS390 WLM request as I'm told that this is the method for providing server load-balancing in a sysplex environment. I wonder why it is not supported in version 4.X. Do you happen to know the long term goal for OS390 load balancing support?
I appreciate your help, Thank you

Cisco IOS SLB or CSM?

I am trying to inform myself if Cisco IOS supports Server Load Balancing (SLB) without the CSM. It appears this software has been integrated into a hardware module known as a Content Switching Module. (CSM)
Aside from cost and being a hardware module (faster) in a IOS based Catalyst 6500, Is there a functional advantage / disadvantage of using the Cisco CSM over Cisco IOS Server Load Balancing or vice versa. Any comments would be appreciated. Thanks.
Mark

IOS SLB shares the same software code base as Cisco IOS and has all the software features sets of Cisco IOS software. IOS SLB is recommended for customers desiring complete integration of SLB technology into traditional Cisco switches and routers.
The CSM is specifically designed to meet the demands of large Internet service providers (ISPs), Co-location facilities, Application service providers (ASPs), and Enterprise web server farms.
These links might help you gain a better understanding:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121limit/121e/121e8/iosslb8e.htm#xtocid32
http://www.cisco.com/en/US/partner/products/hw/modules/ps2706/products_qanda_item09186a0080092384.shtml
http://www.cisco.com/warp/customer/cc/pd/si/casi/ca6000/prodlit/ccsm_ds.htm

IOS SLB Exclusively for Internal Clients

We would like to turn up IOS SLB in dispatched mode on (core) SUP720 MSFCs in an HSRP environment. We would sequester the farm(s) of IIS and Citrix servers on an 'SLB VLAN', with our internal client base on an 'Office VLAN'. All databases and other supporting servers for the SLB servers are also on the 'Office VLAN'.
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Thanks in advance for any input and experiences with this topology. I'm hoping that this is a forest-for-the-trees situation, but I haven't seen many references to an all-internal deployment of either IOS SLB or appliance-based SLBs.
Thanks,
Gene

If you are using dispatched mode, it needs to be L2 adjacent.In dispatched mode, the virtual server address is known to the real servers and IOS SLB redirects packets to the real servers at the media access control (MAC) layer.Phase I of IOS SLB implements dispatch mode only for packet redirection.In this mode, the real servers must be Layer 2 adjacent to the device redirecting packets,not beyond an additional router.

Cisco IOS SLB

Hello Guys,
I am wondering if cisco 3750 Series support Cisco IOS SLB for SMTP protocol, Can anyone help me in this?
Thanks in advance,
Jagdev

Hi Jagdev,
Cisco supports IOS SLB only on Cat 6k, 7x00
Siva

Cat 6500 SupEng MSFC II IOS SLB performance

Hello,
anyone know which are the current cat 6500 Supervisor Engine II MSFC II IOS SLB performance ? I need to know the max tcp/udp cuncurrent active session and the max tcp/udp setup rate.
Thanks a lot.
Best regards
Fabio Bellini

check out the following link for the performance details :
http://www.cisco.com/en/US/products/hw/modules/ps2706/products_data_sheet09186a00800887f3.html

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