The next-hop-self command PLEASE HELP
I have a question about the next hop-self command, i have a topology with 3 routers lets say R1,R2 and R3. Know R1 and R2 are Ebgps neighbors and R2 and R3 are iBgp neighbors. Know lets say i have a loop back address or lan on R3. Do i need to configure Next-hop-self on R2 towords R1 so R1 can ping R3s lans.
I need to be able to know the Logic very well so a clear explenation would be very appreciated.
Sorry, you did say you wanted to understand the logic.
When a BGP router advertises a route to an EBGP peer the next hop in the route is itself. By definition the receiving router must know how to get to that next hop because they are peering with BGP.
When a BGP router receives a route from an EBGP peer if it advertises it to an IBGP peer by default it does not change the next hop IP so the next hop IP is that of the originating router.
So there is a good chance that the IBGP router does not know how to get to that next hop IP.
There are a couple of solutions to this and one of them is to configure the receiving EBGP router to change the next hop IP to itself which obviously the IBGP peer knows how to get because again it has a peering.
Jon
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Hi,
I am learning bgp...need your help...
Connectivity is like as follows:
Router A (ebgp) Router B (ibgp) Router C (ibgp) Router D
when loopback subnet of Router A is received at Router C, defalult with next hop address of outgoing interface of router A.
after configuring next hop self command on router B to C, on Router C then show next hop add outgoing interface of router B. k no prob.
but same subnet isn't received on router D because of ibgp split horizon rule; used route-reflector client on router C. then router D received subnet of Router A; but shows next hop address outgoing interface of router B. even though i used next hop self on router C towards D.; router D didn't show next hop add of router C. Why ??
Its ok i used IGP i.e. EIGRP in between router B, C & D. it works.
=> why next hop self doesn't work in this scenario ?? & is it the reaseon we need to use IGP into IBGP AS ??
--Sandy.Hi,
I agree with Milan, you can use a route-map applied in the outbound direction to rewrite the next-hop.
Another option is to use the "next-hop-self all" (note the keyword all), that will update the next hop of both iBGP and eBGP learned prefixes:
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/command/irg-cr-book/bgp-m1.html#wp4972925610
The use case for this (next-hop-self all) is I see is in a DMVPN Network, but not for an ISP - MPLS/VPN Provider.
Regarding BGP and the need of IGP, think that different protocols have different purposes. The IGP, specially used in large-scale deployments, is used to build the topology and provide reachability to internal prefixes. The IGPs used in large-scale designs, IS-IS/OSPF, are good here because as they are link-state protocols and have a complete view of the network and will detect fast a change and run SPF for a new topology if needed. Furthermore, they have extensions to use MPLS/Traffic Engineering.
Once the topology is build and the routers have reachability to internal prefixes, then you can run iBGP (typically between loopbacks) to provide reachability to external prefixes. BGP is very good to transport a good amount of prefixes, as it is based in TCP. If the IGPs could handle the amount of prefixes can handle BGP, then you would not need iBGP, you would redistribute (which is another option) them to the IGP and we will only have external BGP. However, in order to provide reachability and build and scalable network, you need BGP plus an IGP.
The reason of having the need of an iBGP full mesh is to prevent black-holes in the network. Think that routers A-B-C, A is running iBGP with C, which are edge routers receiving prefixes from other ASN´s. As B is not running BGP, when it receives a packet destined to an external network it will drop that packet as it has no information in the RIB.
There was also an old rule called synchronization that prevented the problem of advertising a black hole to another AS. The rule was that if the prefix is not in the IGP, BGP will not advertise that prefix. So, redistribution solved in the old days the problem of black holes and the rule of sync the problem of advertising them to other ASNs. As the networks got bigger and bigger, there was no point to redistribute the external prefixes to the IGP, so iBGP full-mesh/RRs were deployed and the sync rule disabled.
Hope this helps,
Jose. -
I migrated my software/documents from another laptop so don't have the disk to reinstall. Please help! Can't open any Microsoft Office software, like Word (for 2008), and stuck in a loop?
Whenever I select Word Microsoft Setup Assistant appears, asks for feedback, then after selecting okay (both on saying yes or no to feedback) goes on to a registration page. When I click on this it says I've already registered so I just click okay, and then move on to a update page. After this, if I click on Word, the process repeats itself.
As I said, I don't have the disk to reinstall, and can't find the Office Settings to delete as many pages have suggested I should try. Safe Boot restarting also hasn't worked... Really stuck and need Word very soon for work.
If you can help, that would be great, and feel free to ask any questions about the situation as I'm not an expert here.
Cheers,
JackFirst, export your contact from iCloud.com and save them on your computer in a safe spot some where (like you desktop). Use this to help you do this: http://support.apple.com/kb/PH3606
Next, on both of your devices, go to Settings > iCloud and turn on contacts and select Merge. Then turn off contacts and select 'Delete form my [device]' when prompted.
Now go back to iCloud.com and select a contact (yes they will all be messed up again) and select Command+A on a Mac or Control+A on a PC to select all of the contacts. Tap the delete key on your keyboard (or right click /control click a contact and select delete).
You iPhone, iPad and iCloud.com should not be empty for contacts.
Go back to Settings > iCloud on both devices and turn on contacts again (you should not see merge this time).
Next, go back to iCloud.com and import your contacts (those exported .vcards). You can either drag and drop them into the empty contacts list in your web browser, or you can use the gear icon to import.
You cleaned up contacts should import correctly into iCloud.com and sync to both of your devices.
Good luck. -
my itunes will not open at all. it occasionally will open but when i plug my iphone into it the program freezes and crashes. please help as soon as possible
i think i might have a solution... i have windows vista and after i installed to latest itunes update everytime i tried to open it it would freeze. I tried everything, including uninstalling itunes and all of its components and reinstalled it numerous times. So i went to the itunes folder in my folders, not on itunes, and i deleted my itunes library and playlists. After that it worked just fine, all of my music was deleted but luckily i had my files saved elsewhere.
I hope this helped! I know its frustrating and APPLE/ITUNES NEED TO FIX THE PROBLEM!!!! -
Network address as the next hop address in ip route statement???
Hi All,
I am confused about ip route statements in the following Cisco document.
Configuring ISDN DDR with Dialer Profiles
Document ID: 9568
http://www.cisco.com/warp/public/793/access_dial/ddr_dialer_profile.html
The statements are;
ip route 172.22.0.0 255.255.0.0 172.22.80.0
ip route 172.22.80.0 255.255.255.0 Dialer1
Why does it use network address as next hop address on the first line?
And it is a source network address on the second line.
Please suggest me.
Thanks a lot,
NitassWhen you specify a network address as next hop in a ip route statement, the router does recursive lookup. When it matches a packet for a network other than 172.22.80.0, it will match the router 172.22.0.0 and the route basically says use 172.22.80.0 as the next hop. Now the router looks up the routing table for how to reach 172.22.80.0 and ends up routing via Dialer 1.
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I changed my Apple ID and password and now it says the ID has been dissabled, please help
i need help with ipod touch 2g. i changed the apple id and password and now it says the id has been dissabled.
please help.Try resetting your passord. See:
Apple ID: "This Apple ID has been disabled for security reasons" alert appears
Next contact iTunes
Apple - Support - iTunes - Contact Us -
How do I find out how many files I have, as an earlier version of iTunes told you at the bottom of the screen.
Can anyone please help me with this so I know how many music files or video files I have in my collection.Have a look here...
http://osxdaily.com/2012/11/29/5-tips-make-itunes-look-normal/ -
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Download a free app from the App Store. Once it downloads, your other apps should work properly again. -
HEY GUYS I AM USING AN IPHONE 3g and when i connect my device to my laptop a dialog box appears saying that an update of 4.2 is available so went for it.after the firmware is downloaded via itunes it shows that the firmware is invalid!.please help.
AND ALSO I HAVE HEARD THAT THE IPHONE 3G CANNOT BE UPDATED TO IOS 4.2!IS IT TRUE???
PLEASE HELP ME.This means that the phone you have was software unlocked to use on any carrier, or hacked. When you installed the update it restored the lock that originaly came with your phone. Not much you can do now. Apple will not support hacked phones. You will need to find out the carrier your phone is locked to and see if they offer official unlocking, or start googling to see if you can find a way to unlock 4.2.
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How do I delete movies from iTunes library? I have moved them to the iCloud and now only seem to have the option to hide the icon in iCloud. I am sure I chose poorly at the 'keep file' window. Please help. My Brain hurts… 18 plus movies need to go…. Thank you.
Instead of removing the music from the cloud or the iTunes library why not shuffle your music using a Smart Playlist which excludes the holiday music, or tracks that are not checked. For example, use this very simple Smart Playlist:
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I can't sync any new songs to my iPod, when i plug it in my computer I don't see the iPod icon on iTunes, please help.
iOS: Device not recognized in iTunes for Windows
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I signed into my apple account by iTunes and try to remove credit card information. However, I do not see None option in the payment type section. Please help.
iTunes Store Support
http://www.apple.com/emea/support/itunes/contact.html -
I can not update several of my apps that i have purchased a while back in my Apps Store on my MacPro. Because it keeps using my old @me account for iTunes and i don't remember the password or security question, Please help?
Hi AlphaCentori,
If you are having issues accessing the Apple ID that was used to originally purchase those apps, you may find the following article helpful:
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http://support.apple.com/kb/ht5312
Regards,
- Brenden -
I entered new fields in a form that was created last year to update it. However, now when I view the responses, the headings are listed as Column 1, Column 5, etc. rather than the name of the heading. Can you please help?
Hi Mike,
CRSE is an OEM Product and for use with a custom application they have written. Unfortunately we don't their reports or how they are connecting, it would appear they were originally built off a SQL and then set to a Dataset in the app or they could be adding the data source at runtime. Lots of variations and without access to the source code to see what they are doing not much we can help you with.
You need to contact the OEM Partner for help in resolving this and find out what you can and need to do to update your SP and work with their canned reports,
Thank you
Don -
Receantly I bought a 4s iPhone with 32gb of capacity. The issue consist in by some way the iTunes or iPhone change the name of the artist to others, it looks like that is check marked some option to auto-recognize the name of the song and artist. Please help, I will really appreciate your quick answer.
Eduardo GV.Hi there, ronyme! Thanks for reaching out about your iPhone 4s. It's a great device. I can see you bought it from your cousin. Have you already taken possession of it? If so, are you in the United States or have you taken the device to Jordan or another country?
DionM_VZW
Follow us on Twitter www.twitter.com/vzwsupport
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