Routing loop avoidance in Link State

"The link state method is not susceptible to routing loops which is an advantage over the distance vector method" Why? How it avoid routing loop?

Link-state protocols like OSPF use reliable flooding mechanisms to ensure that all routers are acting on the basis of the same information. Loops occur when routers act on the basis of inaccurate or old information. That is what link-state protocols avoid. All routers in a link-state database have the same view of the network.
Paresh

Similar Messages

Full routing table exchange in Link State Routing?

In link state routing protocols, full update that happen every 30 minutes, does the routers exchange the whole routing table with each other? Or exchange something else, not full routing table. If not the whole routing table, what they are exchanged?

The interval depends on the routing table. OSPF will send out a fresh copy of the LSA (link-state advertisement) every 30 minutes. ISIS will send it every 20 minutes. Only LSAs are sent, not the routing table.
Paresh

Link State Routing Protocol Question

"In LSP, one router in each area is designated as the authoritative source of routing information (called a designated router). Each area router receives updates from the designated router" Why need designated router? How it work? Why can?t it just broadcast LSP and leant the routing information without the need of designated router? Is designate router the same as backbone or root area in OSPF? Is "area" concept only be used in Link State Routing Protocol OSPF?

hi...
you will find area topology in IS IS also...
here we are using the Area as well as DR and BDR for reducing the LSA flooding in the area... each router in ospf area will send update to the DR on multicast address and then DR will send the multicast update to all other router in the area... here each and every router in the area have the full adjucancy with DR but they are not in the full adjucancy with any other router ...
hope this will help you
rate this post if it helps
regards
Devang

Routing loop concern

Hello all,
We have an MPLS setup with all remote sites connected to site X and site X is directly connected to site Y(datacenter). Note: site Y is not connected to MPLS cloud till now. All the traffic is passing from site X to site Y for accessing servers at datacenter. site X and site Y are connected to each other through Metro E. Now we have new circuit thats being provisioned for site Y(datacenter) that is going to be connected to MPLS cloud directly. We do bgp peering with ISP for MPLS connectivity and Internal routing protocol is Eigrp. We are doing mutual redistribution at each location for propogating routes at each site. Now the concern is when site Y is connected to MPLS and when I will do the route redistribution on site Y with MetroE connected to site X will there be a routing loop occurance or will there be a best path selection based on the metrics calculated and will choose the optimal path.
Need suggestions. Thanks in advance.

Okay no problem, it can be a little daunting when you haven't done it before :-)
1) No this isn't right.
When I refer to remote sites I mean sites other than X or Y.
So you must not allow either X or Y to redistribute any remote site networks into BGP.
There is no need because the remote site networks should never be advertised from X or Y and if you do allow it it will cause you problems.
So assuming you want X and Y to back each other up -
X redistributes it's own subnets from EIGRP into BGP and also Y's but no remote sites.
Y redistributes it's own subnets from EIGRP into BGP and also X's but again no remote sites.
If X and Y were not connected via a dedicated link this would not be an issue but because they are and they are exchanging EIGRP routes via that link they each receive EIGRP routes for the remote sites networks from each other as well as from their own MPLS router which is why you need to filter.
2) You can do the configuration on your CE routers.
MED or AS prepending are the tools you use.
So at X you advertise it's own subnets without any modification. You advertise Y's subnets but change one of the above BGP attributes.
At Y you advertise it's own subnets without any modification and X's subnets you need to modify the BGP attribute again.
This basically means that traffic will go direct to X or Y as long as their MPLS links are up.
Either should work although it may be worth having a quick chat with your provider and tell them what you are doing to make sure they are not doing anything that would override your settings.
Apart from that internally the L3 switches in X and Y should see their own MPLS routers as the best path to all remote sites because from your description the L3 switch is only one hop away from the MPLS router in X and Y whereas to go via the dedicated link would mean more hops.
I'm assuming it means more hops.
Quick way to check is do a traceroute from X L3 switch to it's MPLS router and then a traceroute from X L3 switch to Y MPLS router and hopefully there should be more hops going to Y.
Do the same from the Y L3 switch.
If it is the same number of hops then you may have to modify the EIGRP metrics.
All of the above about redistribution only applies to EIGRP to BGP.
There is nothing to do about the BGP to EIGRP redistribution.
Concentrate on the redistribution issue because that could seriously affect your network in terms of it working properly.
Regarding the second issue have a chat with your provider about the MED and AS prepending just to clear it with them.
It's not a given that traffic would go in the wrong site, it might, but it wouldn't be the end of the world if you got it wrong temporarily because traffic is doing exactly that to and from the DC at the moment ie. it goes into X and across to Y.
By all means come back if you need more help but like I say focus on the redistribution issue because that really does need addressing.
Jon

Loop Avoidance

Distance vector uses split horizon and route poisoning for loop avoidance. What techniques are used in MPLS for loop avoidance?
Thanks,
John

Just like TTL in the IP header, MPLS header also has a 1-byte TTL
When an IP packet is first labelled, the (IP TTL -1) is copied to the MPLS TTL
When the label is removed, the MPLS TTL value of removed label is copied to the either MPLS TTL of inner label or IP TTL field (if no inner label), provided
MPLS TTL < IP TTL
And then, IP TTL is decremented
HTH

LSAs in link state protocols

Lets say we have a stable network and we are using a link-state routing protocol. Then something fails. Will the routers reflood ALL LSAs when one LSA changes or only refloods the changed LSAs?

Francisco
Only the LSA's that have changed will be advetised out. That is one of the big advantages of OSPF in that only affected links are advertised rather than the entire OSPF database.
Jon

More than one style for a single link state?

RH 8 outputting CHM
Hello,
Is it possible to define more than one style for a single link state?
For example, I would like a link in the footer of my master page to be smaller than the links that appear in the body of my topics. I want to retain behavior, and simply change the point size.
I can't simply hand format in Design mode, because my link is within a script. Or, am I missing something easy here?
Thanks much.

I'm pleased to say I figured out how to change the formatting of a hyperlink embedded within a script.
Within the script, I used a var string to reproduce the text in my link. Then I used another var to change the string size.
So, here's the part of my script that produces what I'm after:
var mailDisplay = 'Was this information helpful? ';
var str = 'Was this information helpful?';
var mailDisplay = str.fontsize("1");
Upon generation of the CHM, the script trumps the CSS. It's a beautiful thing.

How to restore visited link state to unvisited

Hi all -
I have a pseudoclass which nicely shows a gray background
after being
visited.
After clicking in ie6 browser, the links remain gray forever!
I am unable to view in the pre-visited state to show a client
sitting next
to me.
I am viewing on my local machine
There are no cookies being set
Flushing cache doesn't do it
Closing browser doesn't do it
Even rebooting the machine doesn't do it
I guess my question is, "where is my WinXP machine
remembering the visited
state?"
Anybody know this one? Many thanks
CSS follows
a.inactive
{border: 1px solid #000000;color: #000000;text-decoration:
none;padding: 4px
7px
a.inactive:visited
{border-color: #000000; text-decoration: none;background:
#CCCCCC; color:
#000
a.inactive:hover
{border-color: #000000; text-decoration: none;background:
#B30000; color:
#fff

A: How to restore visited link state to unvisited

Michael
Many thanks for the browser information and for polishing the
CSS
It is indeed appreciated.
"Michael Fesser" <[email protected]> wrote in message
news:[email protected]..
> .oO(Ken Binney)
>
>>I have a pseudoclass which nicely shows a gray
background after being
>>visited.
>>After clicking in ie6 browser, the links remain gray
forever!
>>I am unable to view in the pre-visited state to show
a client sitting next
>>to me.
>>
>>I am viewing on my local machine
>>There are no cookies being set
>>Flushing cache doesn't do it
>>Closing browser doesn't do it
>>Even rebooting the machine doesn't do it
>
> Clear the browser history.
>
>>I guess my question is, "where is my WinXP machine
remembering the visited
>>state?"
>>Anybody know this one? Many thanks
>>
>>CSS follows
>>
>>a.inactive
>>{border: 1px solid #000000;color:
#000000;text-decoration: none;padding:
>>4px
>>7px
>>}
>>a.inactive:visited
>>{border-color: #000000; text-decoration:
none;background: #CCCCCC; color:
>>#000
>>}
>>a.inactive:hover
>>{border-color: #000000; text-decoration:
none;background: #B30000; color:
>>#fff
>>}
>
> A bit shorter:
>
> a.inactive {border: 1px solid #000; color: #000;
text-decoration: none;
> padding: 4px 7px}
> a.inactive:visited {background: #CCC}
> a.inactive:hover {background: #B30000; color: #FFF}
>
> should do the same.
>
> Micha

Is there a way to link state buttons?

Hi, I'd like to know if there's a way to link state buttons to activate their hover state together. For instance, when the link 'Pioneers of Design' is hovered over it turns red and links to another page. The yellow image loses the 25% white opaque screen on it when it's in hover state and also links to the same page. Both are in separate state buttons. Is there a way to link the two so that when I hover over the image the screen disappears but also turns the pioneers link red at the same time and vice versa when hovering over the pioneers link? I know both can be put into a state button together but that means that the massive space in between the image and text would create the hover state as apposed to only occurring when hovering over one or the other. Also, I don't know what would happen to this because the text links stay fixed when scrolling and the image links do not. Is there a way to do what I'm talking about? Thanks.
I have the latest version of Muse CC 2014

There's no built-in way to do disjointed rollovers, but if you look it up on the web, you should be able to understand how the respective CSS rules work and implement them as custom HTML or after publishing the site.
Mylenium

Optimize report script having many Link statements

Hi,
I have a report script in Essbase which uses around 10 <Link statements to extract level 1 entity members from decendants of specific entity members and around 8 <Link statements to extract level 0 account members from decendants of specific account members. I observed that this report script takes almost 10 to 12 hours to execute. After some investigation I found out that ideally a report script should have maximum 5 <Link statements defined; in case if there are more than 5 <Link statements the report script would run very slow.
Following is excerpt from my report script:
<PAGE ("Scenario", "Year")
<ROW("Entity", "Account", "Custom1", "Custom2")
<COLUMN("Period")
For Entity:
<LINK((<LEV("Entity","Lev1,Entity")) AND (<IDESC("Ent001")))
<LINK((<LEV("Entity","Lev1,Entity")) AND (<IDESC("Ent002")))
<LINK((<LEV("Entity","Lev1,Entity")) AND (<IDESC("Ent003")))
For Account:
Link ((<LEV("Account", "Lev0,Account")) AND (<IDESC("Acc001")))
Link ((<LEV("Account", "Lev0,Account")) AND (<IDESC("Acc002")))
Link ((<LEV("Account", "Lev0,Account")) AND (<IDESC("Acc003")))
Could you please help me to fine tune/optimize this report script and suggest an alternate way to write this script without <Link statements so that I could run this report script faster?
Thanks in advance!
AK

You state 10 but show six. Which is it?
As for performance, if you make it just one Entity dimension LINK statement, is it fast?
Following on that, have you tried breaking the report into multiple report scripts? If they are individually faster, you could just concatenate the output files through an OS batch script. The thought of 10 individual report scripts (although I suppose we are potentially talking about more than that but I can't tell based on the information you've provided) could be complicated, but it might be worthwhile from a prototyping perspective.
Have you tried joining them together with a "!" statement. <--What that means is you write a report script and terminate it with a !. Then write another, similar report script and stick a ! on it. And again, and again, etc. Essbase reads to the ! and then goes to the next report script.
Regards,
Cameron Lackpour

Infinite loop in a catch {} statement, should be simple

Hi, I'm trying to take integer input from the console using a Java Scanner object, and I enter an infinite loop if there is an IO error inside the catch statement. Please let me know if you know what I'm doing wrong:
do
try
Problem = false; //this is a bool
start = Input.nextInt(); // Input is a Scanner, start is an Intenger
catch (Exception IOException) {
     Problem = true;
     System.out.println("Bad value.\n");
     //The infinite loop is inside this statement.
while (Problem == true);
This code block is intended to take integer input, then, if there's an IO error, try to do it again, indefinitely, until it has successfully given Start a value. As it stands, if executed, if there is not an IO error, it works; if there is an IO error it enters an infinite loop in the catch statement. Please forgive my incompetence, any help is appreciated :)

Hi, thanks for the advice to both of you, your suggestion that it is stuck seems to be correct.
I add to the catch statement:
Input = new Scanner(System.in);
To reset it, and it works now. This is probably not the best way to do things, but I'm just a student and it's for a homework assignment that does not require try / catch / for so it works for this, thank you for the help! :)

Link State Tracking in Cisco ASA

Dear ASA Guru,
Is there any feature like Link State Tracking in Catalyst for Cisco ASA. I want to shutdown another interface if one interface is down in Cisco ASA.
Best Regards,
Rizal Ferdiyan

AFAIK - this is not an available feature.
HTH>

Is it possible to put a loop inside a CREATE statement?

Hi,
Is it possible to put a for loop inside a Create statement? Obviously, I've tried it and am getting errors, but I just want to know is it at all possible!?
I want to create a dynamic table where the number of fields is dependent on the number of items the user enters!
This is what I have tried, but it tells me:Error #: 204 : illegal start of expression
String createDatabase = "CREATE TABLE " TheTopic
for (int i=0; i < ListBox.getModel().getSize(); i++)
"(Item"+i+" VarChar(20))";
stmt.executeUpdate(createDatabase);
Is there anyother way of doing what I am trying to do?

>
Is there anyother way of doing what I am trying to do?You might want to reconsider your design unless you are creating software to manager, rather than use, a database.
If managing then, obviously, the user would want to create tables, delete them, etc.
But if using then managing these tables is going to be a problem. If so you should first examine that you really want to do this. If yes, then consider a meta-data design. A meta design might look like.
    Table_Name
         Table_id
         Table_name
    Table_Field
         Field_id
         Table_id
         Field_name
         Field_type
    Table_Value
         Value_id
         Field_id
         Value_value
With the above instead of creating a new table each time, you just add entries to the first and second tables.

500 5.4.6 Data command failed: Routing loop detected

I have recently installed OCS 10.1.2 on single box and configured email server. initially i could send email from web client to other domains. Later I made an MX entry in the named server to send and receive emails to the Oracle email server. At that moment also I could send emails to other domains from web client.
I then configured my email on outlook with smtp and pop server pointing to my hosted server. When I send emails to other domain from outlook I received and error "[550] 5.7.1 Rcpt command failed: Mail denied due to site's policy". I searched the forum and found a solution to take care of it. The message id is 1146225, where in I did the following
Enable Routing Control : active
allow message relay : true
allow message relay domain : *
flag process: -l
Recipient Rewriting Rules: $*@your host target smtp,$1@your domain target smtp,
example:
$*@mail.sinux.com.pe,$[email protected],
you should change the next value in smtp outbound
rele smtp : ip of your source mail or relay :port smtp
flag process: -l
After restarting the SMTP inbound and outbound server I didnt get the above error but after few days got a email saying message could not be delivered to other domains (though the message was delivered to my domain) and the errror says "500 5.4.6 Data command failed: Routing loop detected"
Any ideas to resolve it.
Warm regards,
Vipul

Hey adminmilou,
Please reach out to our direct support via live chat and we will be able to look into this further: http://helpx.adobe.com/contact.html (select Business Catalyst).

LACP or Link State Tracking over VPLS?

Hi all!
I have 2 sites connected with VPLS. Both sites are now having a 2nd VPLS circuit installed (with a different carrier) for redundancy/failover. I've got a Catalyst 3750 at each end to work with.
My question: what's the best way to configure the 3750's? I was thinking either LACP with 2 physical interfaces (one for each VPLS line) - in which case traffic would be balanced across them, which is fine.
OR I could use Link State Tracking, such that if 1 link fails it would failover. Though I'm new to Link State Tracking so I don't know if this would actually work over VPLS.
Your thoughts are very appreciated.

Link state tracking, also known as trunk failover, provides Layer 2 redundancy in the network when used in conjunction with server network interface card (NIC) adapter teaming. Link-state tracking is used to mirror the state of the ports that carry upstream traffic from connected hosts and servers, and to allow the failover of the server traffic to an operational link on another Cisco Ethernet switch. Check out the following link for more information on link state tracking :
http://www.cisco.com/en/US/products/ps6406/products_configuration_guide_chapter09186a00805a75e0.html#wp1285238
Hope this helps.

Routing loop avoidance in Link State

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