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Topic: Flapping router

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	Router - Wikipedia, the free encyclopedia
		A router is a computer networking device that forwards data packets across a network toward their destinations, through a process known as routing.
		Large modern routers have thus come to resemble telephone switches, with whose technology they are currently converging and may eventually replace, whilst small routers have become a common household item.
		A router is normally used to connect at least two networks, but a special variety of router is the one-armed router, used to route packets in a virtual LAN environment.
	en.wikipedia.org /wiki/Router (1118 words)

	Router (Site not responding. Last check: 2007-10-24)
		A router consists of a computer networking device that determines the next network point to which to forward a data packet toward its destination, a process known as routing.
		A router must be connected to at least two networkss, or it will have nothing to route.
		A special variety of router is the one-armed router used to route packets in a virtual LAN environment.
	bopedia.com /en/wikipedia/r/ro/router.html (268 words)

	Route flapping - Wikipedia, the free encyclopedia
		In computer networking and telecommunications, route flapping occurs when a router alternately advertises a destination network first via one route then another.
		Route flapping is caused by pathological conditions (hardware errors, software errors, configuration errors, unreliable connections, etc.) within the network which cause certain reachability information to be repeatedly advertised and withdrawn.
		Route flapping often forces a router to recalculate a new or preferred route to a particular network, while traffic destined for that network is in transit through the router.
	en.wikipedia.org /wiki/Flapping_router (137 words)

	flap - definition by dict.die.net
		flap, and E. flap, v.] Anything broad and limber that hangs loose, or that is attached by one side or end and is easily moved; as, the flap of a garment.
		Flap tile, a tile with a bent up portion, to turn a corner or catch a drip.
		Flap valve (Mech.), a valve which opens and shuts upon one hinged side; a clack valve.
	dict.die.net /flap (430 words)

	yu-routing-scaling-04.txt-61773.txt
		Route flapping refers to frequent routing updates occurring due to network instability, for example, when the state of a physical link in the network is fluctuating, or when a BGP session is torn down and re-established numerous time within a short period of time.
		Flooding is the process by which a router distributes its self- originated LSA to the rest of the routers in the area in case of any link state change.
		One general concern with the use of an RS router is the possibility of a mismatch of routing connectivity and the physical connectivity.
	ietfreport.isoc.org /idref/draft-yu-routing-scaling (7835 words)

	Router (Linux Reviews)
		A router is a computer networking device that forwards data packets across an internetwork toward their destinations, through a process known as routing.
		A router is essentially different from a switch that connects devices to form a Local Area Network (LAN).
		Routers connect networks together the way that onramps or major intersections connect streets to both highways and freeways, etc. The street signs at the intersection (routing table) show which way the packets need to flow.
	linuxreviews.org /dictionary/Router (860 words)

	Network Test :: Lone Router Test Outline
		Router interfaces will be configured with IP addresses 192.1.XXX.254, where XXX is the number of the port.
		Router A will use ports 1-12; Router D will use ports 13-24; Router B will use ports 25-36; and router C will use ports 37-48.
		The QOSnetics QA Robot tester will be attached to one interface of routers A and B to generate route flapping and to verify table entries at every flap event.
	www.networktest.com /pastmeth/99routemeth.html (836 words)

	Troubleshooting EIGRP > Troubleshooting EIGRP Route Flapping (Site not responding. Last check: 2007-10-24)
		In Figure 7-28, a route of 150.150.0.0/16 in network cloud X gets passed to Router A from Routers B, C, and D. Router A chooses Router C as the next hop to network 150.150.0.0/16 and puts Routers B and D as the feasible successors to the network 150.150.0.0/16.
		The problem happens in Router A where the route timer for the route 150.150.0.0/16 in the routing table is constantly at 00:00:00.
		Router A is simply a result of the problem caused by Router D. After a Cisco IOS Software upgrade on Router D, Router A stops refreshing its routing table timer, as indicated in Example 7-51.
	www.ciscopress.com /articles/article.asp?p=27839&seqNum=5 (1187 words)

	[No title]
		External measurements start with a stimulus from one or more "upstream" routers and end with a specific event causing an advertisement to be sent to a "downstream" peer.
		The objective is to determine whether one route flapping affects the operation of the router.
		Typically, routers in this application are limited by bandwidth rather than route processing A.2 Interprovider peering with transit The DUT exchanges 1.3 D routes with a small number of peers.
	quimby.gnus.org /internet-drafts/draft-ietf-bmwg-bgpbas-00.txt (2236 words)

	Internet Routing Recommendations
		Routers "flap," or lose their ability to route efficiently, for a number of reasons, including configuration errors, network links going up and down, software bugs, and other network problems.
		Route flaps spread from router to router and propagate throughout the network; at the extreme, route flaps have led to the collapse of portions of the Internet.
		BGP Route Flap Damping, by Curtis Villamizer of ANS, Ravi Chandra, Cisco, and Ramesh Govindan, ISI.
	www.merit.edu /~ipma/docs/help.html (1766 words)

	Troubleshooting EIGRP > Troubleshooting EIGRP Neighbor Relationships (Site not responding. Last check: 2007-10-24)
		Router D can't answer Router B's query because Router D is waiting for the router with the IP address of 10.1.5.2 from Serial1/2 (Router E) to re-spond to the query.
		Router A went active for route 20.2.1.0/24 and is waiting for Router B to reply to the query.
		Router D can't reply because it is waiting for Router E to reply to the query.
	www.ciscopress.com /articles/article.asp?p=27839 (5374 words)

	Light Reading - Cisco - Internet Core Router Test - Telecom Report
		The first test examined route flapping, the condition in which numerous routes are withdrawn and re-advertised in rapid succession.
		In the flapping test, we began by bringing up BGP sessions on all interfaces and loading the routers with the same 200,000+ entries used in the baseline tests.
		Sounds good, but a router still has to be able to deal with at least one significant change in table state before this feature kicks in.
	www.lightreading.com /document.asp?doc_id=4009&page_number=12 (961 words)

	IP Event Dampening
		The flapping interface is identified by the router and assigned a penalty for each up and down state change, but the interface is not automatically dampened.
		However, those other routers could still install some routes in their routing tables that are associated with this subnet because those routers recognize that their own interfaces are up and could start forwarding packets to the dampened interface.
		A router with a flapping interface removes the flapping interface from the network until the interface stabilizes, so other routers simply redirect traffic around the affected router until the interface becomes stable, which ensures that the router loses no data packets.
	www.cisco.com /univercd/cc/td/doc/product/software/ios122/122newft/122t/122t13/ftipevdp.htm (3756 words)

	RSVP Integrated Multicast (RIM)
		However, only a router neighboring a receiver is able to calculate the best QoS path from an RVP to the receiver according to receiver's QoS request, while an RVP cannot calculate the path since it cannot get the complete location information and the requests of all receivers.
		Each router that received a Resv message calculates the shortest path tree (SPT) from an RVP to itself, and forwards the Resv message along the reverse path from the RVP to itself, which becomes a part of the tree.
		Router T5 has to change the direction to which it forwards a Resv message, from T3 into T4, since link T3-T5 does not have enough bandwidth.
	www.isoc.org /inet99/proceedings/4b/4b_3.htm (2971 words)

	Guide to Cisco Router Configuration
		The term coined to describe this repeated advertizement and deletion of routes is "route flap" or a router "flapping".
		In the preceding example, router A is configured with one iBGP peer and begins advertizing 3 subnets of the 1.0.0.0 class A. Router B configures one iBGP neighbor and one eBGP neighbor and summarizes routes learned from router A into a single advertizement which is sent to the eBGP peer.
		Such limitations might be due to a lack of adequate memory in the router or a router that does not support the desired protocol.
	www.opennet.ru /soft/cisco-configuration.html (10717 words)

	[No title]
		In the case of only Router and ASE LSAs we normally assume that the number of ASE LSAs in the storm is about 4 times that of the Router LSAs, but the ratio is allowed to change if either the Router or the ASE LSAs have reached their maximum possible value.
		In the case of only Router and Link LSAs (carrying traffic engineering information) we normally assume that the number of Link LSAs in the storm is about 4 times that of the Router LSAs, but the ratio is allowed to change if either the Router or the Link LSAs have reached their maximum possible value.
		Network 1 has 100 routers, 1200 links, maximum number of neighbors per router is 30 and maximum number of adjacencies per router is 50 (same neighbor may have more than one adjacencies).
	www.math.utah.edu /ftp/pub/mirrors/ftp.ietf.org/internet-drafts/draft-ietf-ospf-scalability-05.txt (5457 words)

	HP OpenView's Route Analytics Management System Demonstrations - OSPF Route Flapping - Text Version
		Okay, I can see that 2 routers in particular generated all of the routing control events, so in the case of OSPF here, these are link state announcements from these routers.
		In the case of a larger prefix flapping, say a /24 or a /16, the potential impact of this could be extremely large.
		So what I can conclude here, is that these 2 routers have the default route which points to BGP, so that when the prefixes are unavailable because of the flapping on these core routers the traffic is routed straight out to the internet.
	h41111.www4.hp.com /rams/uk/en/OSPFRouteFlap_txt.html (1447 words)

	Cisco - Border Patrol: BGP
		The weight attribute is local to the router on which it is assigned; it is not propagated in routing updates.
		In route dampening, BGP nodes assign a penalty value to a flapping router, based on the frequency of flaps.
		However, with BGP multipath support enabled on the router, the BGP speaker will install as many as six paths in the IP routing table in instances when the EBGP paths are learned from the same neighboring AS.
	www.cisco.com /warp/public/784/packet/oct98/6.html (1645 words)

	Mind Forums - CCNA Part 5 - IP Routing (Site not responding. Last check: 2007-10-24)
		While the routers are converging (synchronizing their routing tables), no data is passed.
		All routers must be in the same AS in order to communicate.
		Poison reverse is when a router sets the metric for a downed link to infinity (unreachable).
	mindforums.com /forums/showthread.php?threadid=219 (1449 words)

	rfc4222
		The LSA storm causes high CPU and memory utilization at the router causing incoming packets to be delayed or dropped.
		The LSA storm causes high CPU and memory utilization at the router processor causing incoming packets to be delayed or dropped.
		However, a router with a changing ID may flush the old LSAs gradually without causing a storm.
	ietfreport.isoc.org /idref/rfc4222 (4113 words)

	LSAR
		If the LSAR or its link with the router is flapping (going up and down), the associated adjacency can start flapping, triggering SPF calculations around the network.
		Partial adjacency mode: To prevent network-wide SPF calculations when the adjacency between the LSAR and the router is flapping in the full adjacency mode, we can keep the adjacency in an ``intermediate'' state at the router, so that the router does not include a link to the LSAR but still sends LSAs to it.
		Keeping an adjacency in the loading state on a router for a long time might generate alarms, or might cause the router to drop the adjacency.
	www.usenix.org /publications/library/proceedings/nsdi04/tech/full_papers/shaikh/shaikh_html/lsar.html (918 words)

	Router Resiliency (Site not responding. Last check: 2007-10-24)
		Attaining carrier-class router reliability is of prime importance to providers of IP networks and services.
		Network equipment manufacturers have responded to the demand for router resiliency with a number of technologies that promise to deliver "hitless failover" (switching to a backup control card with no router downtime when the primary control card fails) and "hot upgrades" (live, in-service upgrades of router software).
		Note: For many of these tests, the SUT could be a single router or a mesh of interconnected routers.
	advanced.comms.agilent.com /n2x/docs/Journal/SecRoutResiliency.html (750 words)

	ROU from FOLDOC
		Next: route, routed, route flapping, router, routine, routing, routing domain
		Next: routed, route flapping, router, routine, routing, routing domain
		Previous: route, routed, route flapping, router, routine, routing, routing domain
	www.instantweb.com /d/dictionary/foldoc.cgi?query=ROU (590 words)

	VoIP Troubleshooter \| Problems \| Route Flapping
		Routers can occasionally enter a state in which they periodically switch route — typically every few minutes.
		This results in the delay alternately increasing and reducing.
		VoIP Troubleshooter LLC and Contributor are providing this material as-is with no warranty as to correctness or completeness and do not accept any responsibility for any issues or problems of any nature whatsoever that may arise from the use of the material on this site.
	www.voiptroubleshooter.com /problems/routeflap.html (166 words)

	[No title]
		In this approach, BGP router compares with the origin AS in BGP UPDATE and origin AS in IRR database.
		Cache mechanism works as: (1) before queuing to the IRR-DB, BGP router looks up its own cache at first, (2) only the case of not existing cache entry, BGP router queries to the IRR-DB, (3)BGP router inject cache as the reply of IRR-DB (origin AS and prefix).
		BGP router registers prefix in BGP UPDATE and associated origin AS which is replied from IRR-DB in cache.
	www.ietf.org /proceedings/02mar/I-D/draft-kengo-bgp-integrity-check-00.txt (822 words)

	Flapping (Linktionary term)
		When a route in an IP network goes down, the router that knows about the change advertises it to neighboring routers.
		Route flapping is when this occurs rapidly and possibly on a large scale.
		The Internet is protected from route flapping on private networks because private networks advertise only a summary of their internal routes.
	www.linktionary.com /f/flapping.html (165 words)

	SANS - Internet Storm Center - Cooperative Cyber Threat Monitor And Alert System
		Route flapping may result in route dampening (suppression) if the route flaps occur frequently within a short time interval.
		Cisco and Juniper are scheduled to publish announcements about vulnerabilities in the implementation of the BGP code in their respective routers this week.
		Please note that the router at 10.1.1.2 would also have to be configured to use the password a1b2c3d4e5f6g7h8 during the peering session as well.
	isc.sans.org /diary.php?date=2004-04-20 (1069 words)

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