Question

dns and apache and Cisco router

Asked by: fosiul01

Hi,I am trying to design a network for load balancing and redundancy. but don't know where i will face problem , that's why i am looking for comments for problem finding and solution .. from DNS, cicso and apache point of view...

My Goal is :

1. make a load balancing network for incoming http request(www.mydomain.com) and out going http request(internal user).

Please have a look to the network diagram.

Here.
i will have a domain . www.mydomain.com,
and i will create 2 A record which will point to 2 isp(public Ip) and request will come to our network.
so i need load balancing and redundancy.
(From DNS point of view is that the right way ??setup 2 A record with 2 public ip for a domain ??)

NOw when request will come to our network, I want it be load balanced via 2 Cisco router also, if one ISP is down load, http will come via another (isp) router. when 2 isp is up then http request will come via both isp (load balanced)

bellow link will show how to make cisco router for load balanced and redundancy
http://articles.techrepublic.com.com/5100-10878_11-6063344.html
but here i guess both router is using 1 isp line,but i want to use 2 isp line

NOw from Cisco point of view the way i set-up my network, will it work ??with Cisco router 1841 or 1081)
Now for http request point of view , is there any problem ??

I will speak about clustering later on.. but now upper 2 question is my main point of view

Here I just want you guys to pin point problems.Solution can come up later on with other questions..

Thanks for your time and patients

network-diagram.JPG
- 37 KB
Network-diagram

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Asked On: 2009-09-18 at 04:19:31ID24742829
Topics: Domain Name Service (DNS)
,; Network Routers
,; Linux
Participating Experts: 1
Points: 500
Comments: 19

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Answers

by: nociPosted on 2009-09-18 at 05:46:22ID: 25365334

load balancing over 2 ISP's will become difficult.

you ask for a name www say it gives ip1 & ip2
the next query will give ip2 & ip1 (rond robin fashion) this is at all levels in DNS queries (when forwarded to a provider, which uses the same technique etc). (and does a browser reuse a known address or ask a new one every time...etc).
All your remote users will see a different switching preference. (you can help a bit by f.e. user ip1, ip1, ip2; then on average 2/3 of all connections will enter on ip1.

Because the remote user goes over separate networks the routing decision for ip1 or ip2 is out of reach for your organisation....

You can use DNS for failover though: use a DNS record with short (f.e. 60 second TTL). Then utmost 60 seconds after updating DNS the last record will expire all caches in the world. Do prepare for quite a bit more DNS traffic though.

If you can have a private IP registerd with your provider, that will inject BGP records into the internet then you can make use of a virtual IP for your services, no need to use DNS failover then. But both your ISP's have to do the BGP lifting.

by: fosiul01Posted on 2009-09-18 at 05:59:08ID: 25365434

Hi thanks

about your comments :

You can use DNS for failover though: use a DNS record with short (f.e. 60 second TTL). Then utmost 60 seconds after updating DNS the last record will expire all caches in the world. Do prepare for quite a bit more DNS traffic though.

-> with this dns failover, still there would be a problem is not it ?? if https trafiq come via isp1, then suddently isp1 stops so those existing request will fail.. is that right ??

If you can have a private IP registerd with your provider, that will inject BGP records into the internet then you can make use of a virtual IP for your services, no need to use DNS failover then. But both your ISP's have to do the BGP lifting.

-> i never hard of this theory!! will you be able to explan little bit or sent some article ...
I see other company , they have A record of 2 Ip. so are they doing BGP ??

by: fosiul01Posted on 2009-09-18 at 06:04:15ID: 25365473

also, if i have 1 isp then i can do this easily, is not it ??
but i want, 2 isp with always ON website ( because in case if one ISP is down then i need another isp to backup)

what do you suggest ?? what's the best way to perform, how do you do ??

by: nociPosted on 2009-09-18 at 06:51:26ID: 25365917

@1: Yes, max. 60 seconds after you update the DNS the will get the right entry, you could try shorter TTL times.

@2 how does an internet router know the way to your common IP address (which should not be a private IP (in the sense of the RFC1918 addresses (10/8; 172.16/12; 192.168/16) but a public IP that doesn't belong to either provider.

You need an AS number from IANA, and an IP(range?) from RIPE/ARIN/???
You need to be able to publish this address with the access points needed.

Here is a howto on the subject, please read it first....
http://articles.techrepublic.com.com/5100-10878_11-1039765.html

Ever thought of finding a hosting partner that can handle/has handled the internet traffic redundcy shuffle allready?
Any decent hosting outfit should be able to do this. (maybe not the el'cheapo's)

Also with 1 isp there might be enough trouble to get it right, you will ALLWAYS need some support on the outside.

And 2 ipaddresses don't imply BGP, using one address space over several independant connects implies BGP.
2 Ip addresses might as well be 2 (sets of ) physical server(s) spread over 2 separated data centers with some means of mirroring.

by: fosiul01Posted on 2009-09-18 at 07:16:43ID: 25366184

Ok so normal round robin is not a solution.... for good web service, right ??

Ok Again.. i am totally new of this cocept , so please bare with me
the article you sent me, thats really good. but what is
what is ASN ?? why i need to get it from ARIN ??

Example : doming www.mydomain.com ,
Zone Record:
www IN A 202.101.303.202
www IN A 88.66.99.56

so with this BGP, those A record would be changed ?? so will i not be able to use public IP ??

your comments :
Ever thought of finding a hosting partner that can handle/has handled the internet traffic redundcy shuffle allready?
-> You meants instead of doing myself , try to find a hosting partner who already developed this ???

if yes, then no... i want to learn this. I had an interview few days ago, and that interview made me mad. currently in our company we don't do redundancy, but if i can implement this design then i will tell my company to implement this. basically i want to do this by myself. what ever it takes.

Your comments :
2 Ip addresses might as well be 2 (sets of ) physical server(s) spread over 2 separated data centers with some means of mirroring.

-> Yes it could be , but if you set 2 A record like this

Example : doming www.mydomain.com ,
Zone Record:
www IN A 202.101.303.202
www IN A 88.66.99.56

then if both DATACENTRE is Up and runing, then SErver A (202.101.303.202) which is located Datacentre A and SErver B (88.66.99.56) which is located Datacentre B

Now as a rule , as you said earlier, First set of http trafiq will go to DataCentre A, 2nd set of request will go to DataCentre B

right ??
Now if DataCentreA is down, all trafiq will go to Datacentre B, which is allright, but again, what will happend those trafiq which already set to DatacentreA before line is down, so those request will get Error. which i dont want. and i guess they use some sort of BGP or something else to prevent those..

right ?

but from my point of view is, suppose if i have only one centre and i want full redundancy then you need redundancy in every point is not it ?? From Isp -> router -> server , is not it ???

what you use ?? BGP ??

by: nociPosted on 2009-09-18 at 07:41:17ID: 25366454

ASN is Autonomous System number -- it uniquely defines your address space (i.e. Your network).
ASN you would get from IANA (http://www.iana.org/) as they manage the AS table.
ARIN supplies an IP address for North america, RIPE does the same for Europe + Middle East,
see: http://www.iana.org/numbers/

Example 1
If you bouth the public address 1.2.3.4, then with BGP you woud install 1.2.3.4 as the ip address for your www.
And use BGP (it's an IP routing method, (layer 3) and has nothing to do with www etc.) to move the traffic from the internet to your two entry points of your network (identified by your AS number).

Example 2:
No first query answer will give order Server A, Server B; next query will be Server B, Server A etc. It depends on DNS Querying if a browser queries DNS for every request then the main page could come from A, the first picture from B, the 2nd picture from A etc. You can hardly predict how systems would be accessed
No you need to update the DNS to have all traffic go to one place..., there is no automation there.

try f.e. 'dig google.com'
you will see that addresses rotate, if asked in succession.

BGP is too expensive for private use. ALL bgp routers have ALL internet forwarding routes in memory, you would need a BIIIIIIG router to manage that (twice) and then internal you will need routing too (OSPF based).
BGP only advertises how others can reach your network, where you prefer it (priority) and if a link goes down, the OTHER BGP routers will miss an update and remove a route....
(You can try this in a small simulated network using f.e. quagga (formerly zebra) http://www.quagga.net and some virtual linux systems )

by: fosiul01Posted on 2009-09-18 at 07:45:34ID: 25366498

yes, i agree, i was reading about BGP, its not an ideal for small business, it could be for big isp or similier type of organization

http://www.quagga.net, this link does not work

so whats the solution for me ??

by: fosiul01Posted on 2009-09-18 at 08:02:54ID: 25366698

Ok i might have some idea how it could be done..

Suppose if i have a device which will works as dns server aswell and it will hold the dns record , and this device will have a 2 wan port. when it will realized that One isp is down, it will edit the dns record and will just keep one,
example network using powerlink :http://www.ecessa.com/pages/solutions/solutions_technology_ispfailover.php

but i need cisco basae solution... with 2 router ..

if i use a server , then that server will have a script, this will script wil check both isp line, as soon as it will see one isp is down, it will edit the dns record and will keep the runnign one

but then i need the load balancing aswell .....

LOL!! i want to much but i have little idea!!
hence you guys here, is not it!!

but whats your solution ?? how you do ???

by: nociPosted on 2009-09-18 at 08:06:29ID: 25366729

The wiki does work...
http://wiki.quagga.net/

download:
http://linux.softpedia.com/progDownload/quagga-Download-10358.html

Other source:
https://quagga.datacore.ch/DCwiki.zebra/Wiki.jsp?page=Main

by: fosiul01Posted on 2009-09-18 at 08:10:45ID: 25366774

Ok i will try that one

so you using BGP in your organization ???

by: fosiul01Posted on 2009-09-18 at 08:28:04ID: 25366960

read this pd file

its a hardware base solution which will hold the Dns entry

but i want something for cisco router base solution ..

i will create another question as cisco zone, if you know any cisco brand can do then answer to that one,
its not good to ask too many in one question

PowerLink-and-Authoritative-DNS.pdf
- 242 KB
powerlink

by: fosiul01Posted on 2009-09-18 at 09:22:36ID: 25367546

have a look to this one

http://www.experts-exchange.com/Hardware/Networking_Hardware/Routers/Q_24743652.html

also read the pdf file, its very related to what i want but i want cisco base solution ..

you did not tel me, how you solving this situation ?? do you using BGP ??

by: nociPosted on 2009-09-18 at 10:38:34ID: 25368141

(I was driving home since 17:00 my time).
No i don't use BGP it only makes sense if you want your own network accessible through multiple access paths, so no i don't use it. Organisations I work for are relatively big, they have big networks of their own, they are big enough to get a deal with a provider that arranges all backup ... (it's a bit like selecting a good hosting provider).

regarding the ecessa box... This is "just a DNS server" with one added extra; it only answers if links are available. Could be done in linux... Make a DNS server , make it the authoritive server with the nameservice provider.. (ie. set the ns records at Net.Sol for .com & .org f.e.).
On that box make an empty zone, with only the static info (MX, NS rr records).
Then run the following script for each provider:, "

#X = provider
while true; do
ping $upstream[X]
if there was response then add dynamic address for $public_ip[X]
else remove dynamic address for $public_ip[X]
sleep 5
done

the DNS server will do the remaining part.

As you need an DNS server this cannot be done in a CISCO router, but take your avarage Linux Distro and you;'re almost set.

by: fosiul01Posted on 2009-09-18 at 12:50:13ID: 25369382

Sorry i was breaking my fast...

so you saying With Cisco router you can do what i am trying to achive ??

if i use cisco router, then i will have to edit zone record manualy via script ??

is that 100% correct ??

if even i edit zone record by script and with very short ttl like 1M

is there any change for user to get http error ?? this is my main concern

by: nociPosted on 2009-09-18 at 13:17:11ID: 25369616

yes there allways will be a chance a user will see an error. If it fails in the middle of a transfer that cannot be helped (not this way).
And NO Cisco has NO DNS ==> you cannot just use CISCO to do this.
A cisco can direct IP packets & filter them not update above layer 3 services like DNS.

A linux system with DNS and a little bit of scripting can do it, if you can have a cisco to sit in between the linux system and the Internet router well ...

ISP1====ACCESS-ROUTER=====[Cisco?]============[cisco?]======ACCESS-ROUTER======IPS2
           ISP1                     |       |                    ISP2
                                 +------+ +-------+
                                 |Linux | |Other  | 
                                 | DNS  | |Servers|
                                 +------+ +-------+
wether there is a cisco or not is not really relevant.

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by: fosiul01Posted on 2009-09-18 at 13:29:33ID: 25369725

hmmmmm Ok its clearing up now...
but you said, : If it fails in the middle of a transfer that cannot be helped (not this way).

so whats other way ?? how can you make it 100% transparent ??

Example if i use power link router ( the pdf file i have attached) which has built-in dns zone and can zone edit facilities, still i cant assure 100% transparent, right ???

if yes, then whats other way ??

Sorry to ask soo many question, but i need to clearup this things ..

by: fosiul01Posted on 2009-09-18 at 15:18:06ID: 25370452

but since i am following our idea , i will add couple of question for next few days to grasp the concept properly, so please stay with me for next few days

thansk

by: fosiul01Posted on 2009-09-21 at 01:51:36ID: 25381139

Hi.
This is another one, if you have time please have a look
http://www.experts-exchange.com/Hardware/Networking_Hardware/Routers/Q_24747724.html

by: nociPosted on 2009-09-21 at 12:02:52ID: 25386304

You need multiple independent redundant pipe's (connections to ISP) per ISP, have a firewall/router combination that can handle statefull failover from one box to another.
The independent pipes need to act as an Aggregate link.

I.E. Very expensive as well in procurement as well as maintaining.

20120131-EE-VQP-002

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dns and apache and Cisco router

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