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R1(config)# int s1/0 R1(config-if)# encapsulation ppp R1(config-if)# ppp multilink group 1 R1(config-if)# no shut R1(config-if)# do sh run int s1/0 Building configuration... Current configuration : 108 bytes! interface Serial1/0 no ip address encapsulation ppp serial restart-delay 0 ppp multilink group 1 end R1(config-if)# int s1/1 R1(config-if)# encapsulation ppp R1(config-if)# ppp multilink group 1 R1(config-if)# no shut R1(config-if)# do sh run int s1/1 Building configuration... Current configuration : 118 bytes! interface Serial1/1 no ip address encapsulation ppp serial restart-delay 0 ppp multilink group 1 end R1(config-if)# int multilink 1 After created the multilink interface, some commands are automatically added in serial interfaces and multilink interface R1(config-if)# do sh run int s1/0 Building configuration... Current configuration : 123 bytes! interface Serial1/0 no ip address encapsulation ppp serial restart-delay 0 ppp multilink ppp multilink group 1 end R1(config-if)#

RIP Timers The Cisco implementation of RIP uses four timers: Update Invalid Flush Holddown RIP sends its full routing table out all configured interfaces. The table is sent periodically as a broadcast (255.255.255.255) for Ver.1 and multicast (224.0.0.9) for Ver.2 to all hosts. Update Timer The update timer specifies the frequency of the periodic broadcasts. By default, the update timer is set to 30 seconds. Each route has a timeout value associated with it. The timeout gets reset every time the router receives a routing update containing the route. Invalid Timer When the timeout value expires, the route is marked as unreachable because it is marked invalid. The router marks the route invalid by setting the metric to 16. The route is retained in the routing table. By default, the invalid timer is 180 seconds, or six updates periods (30 x 6 = 180). Flush Timer A route entry marked as invalid is retained in the routing table until the flush timer expires. By default, the flush timer is 2

Where IPv4 has ARP, IPv6 has NDP, the neighbour discovery protocol. For simple purposes, NDP and ARP are very similar: one node sends out a request packet (called a neighbour solicitation in NDP), and the node it was looking for sends back a reply (neighbour advertisement) giving its link-layer address. NDP is part of ICMPv6, unlike ARP, which doesn't even run over IP. NDP also uses multicast rather than broadcast packets, and that deserves a little more explanation. For each unicast address it responds to, each host listens on a solicited-node multicast address. The solicited-node multicast address for a given unicast address is constructed by taking the last three octets of the unicast address and prepending FF02::1:FF00:0000/104. Thus, the solicited-node multicast address of 2001:630:200:8100:02C0:4FFF:FE68:12CB is FF02::1:FF68:12CB. It's the solicited-node multicast address that a node uses as the destination of a neighbour solicitation packet. This use of multicast means t

Queueing is for Congestion Management. Custom Queueing: With CQ, bandwidth is allocated proportionally for each different class of traffic, By default, each cycling, dequeque 1500 bytes for each queue. CQ allows you to specify the number of bytes or packets to be drawn from the queue http://www.ccietalk.com/2008/12/15/custom-queueing Configuration: queue-list command, then apply under interface using custom-queue-list • Defining the Custom Queue List (Required) • Specifying the Maximum Size of the Custom Queues (Optional) • Assigning Packets to Custom Queues (Required) • Monitoring Custom Queue Lists (Optional) Class-Based Weighted Fair Queueing (CBWFQ) Class-based weighted fair queueing (CBWFQ) extends the standard WFQ functionality to provide support for user-defined traffic classes. For CBWFQ, you define traffic classes based on match criteria including protocols, access control lists (ACLs), and input interfaces. First In First Out (FIFO) Queueing First In, First Out (FIFO) Queuei

Traffic Shaping doesn't drop voilated traffic, it typically delay the excess traffic using buffer or queueing mechanism. Traffic shaping controls the speed of traffic leaving an interface. Cisco has three types traffic shaping: Class-Based Traffic Shaping, Generic Traffic Shaping (GTS), and Frame Relay Traffic Shaping (FRTS). Generic Traffic Shapping: use traffic-shape command at interface level. Frame Relay Traffic Shaping: can shape traffic per DLCI. 1. Difine map-class with frame-relay command 2. use frame-relay traffic-shaping command at phsical interface to enable Frame Relay Traffic Shaping. 3. at subinterface, call class in frame-relay interface-dlci command.

Priority Queuing has four queues: High, Medium, Normal and Low. High Queue must be empties before the router serves Medium Queue, then Medium Queue must be emptied before serve Normal Queue, and so on. Configuration: Priority-list Then in interface config mode: Priority-group Verify: Show queueing References: http://www.cisco.com/en/US/docs/ios/12_1/qos/configuration/guide/qcdconmg.html#wp1001400 http://www.cisco.com/en/US/docs/ios/12_1/qos/configuration/guide/qcdpq.html

Here is the script to ping many IPs from a router, run this in tclsh. foreach IP { Ip1 Ip2 Ip3 ... IP100 }{ping $IP}

on a multiaccess LAN, DR is responsible for "PIM" Register/Prune messages toward RP. IGMP Querier is responsible for IGMP "host-query" messages. With IGMPv1, since there is no concept of Querier, PIM DR typically serves both the PIM routers and IGMP hosts (think of it as an additional responsibility). With IGMPv2, there IS an election, so router with lower ip address serves the hosts (as an IGMP Querier) and router with higher ip address serves PIM routers (as PIM-DR). The winner of Assert process is responsible for forwading multicast onto LAN

This command simulates the end client to join a multicast group, it responses to PING, the router executes PING simulates the multicast Source.

In PIM Sparse mode, a router needs send Join message to the RP to receive multicast traffic. With AutoRP, the mapping agent send RP info using 224.0.1.40, however, since PIM is in sparse mode, the 224.0.1.40 multicast won't flood in entire network, other router wants to receive this traffic but isn't aware of any RP to send join message, this is chicken-and-egg problem. There are two solutions: 1. PIM Sparse-Dense mode a router uses Dense mode if it has no info where the RP is, so 224.0.1.40 traffic can flood entire network in dense mode, then the router switch to Sparse mode since it knows RP. 2. PIM autorp listener. This command causes the router flood 224.0.1.40 traffic out all interfaces. AutoRP is enabled on the Cisco router by default, so all routers have the following mroute by default: (*, 224.0.1.40), 00:07:57/00:00:07, RP 0.0.0.0, flags: DP   Incoming interface: Null, RPF nbr 0.0.0.0   Outgoing interface list: Null In case we don't use AutoRP, we can

Tc -- Time interval, Tc=Bc/CIR Bc -- Committed burst size, the bits can be sent per Tc interval. It specifies in bits (or bytes). Also called Sustained. CIR -- Committed information rate, the bits can be sent per second. Also called Mean rate. So Bc and CIR are same thing but measured in different way. Be -- Excess burst size, bits can be sent per second beyond Bc after a period of inactivity. Shaped rate -- bits per second, it may or may not be set to CIR. At service provider side, CIR means the "guaranteed” rate of the circuit based on the SLA. At client side, “CIR” in the context of shaping simply means the target average rate. The actually speed of sending date can only be the line speed, to shape or policer the date to a lower speed, for example, to 10M of 100M Ethernet interface, the way the interface does is to send the data at line speed a very short period then stop, this send/stop is a interval called Tc, which can be 1/8 to 1/125 second. Shorter interval m

1. When a multicast application launches on a host, a IGMP Report sends out, this is join message. 2. A multicast router periodically sends out IGMP General Query to 224.0.0.1. 3. A multicast host response the query by sending out IGMP Report to the group address it is listening on. 4. On a LAN, a host uses MRT to suppress its IGMP Report when it sees other host sends IGMP report already. 5. A host sends Leave message when it is no longer interested in recevieing multicase traffic, the router will sends Group-Specific Query when receives the Leavel message, and expecting any hosts still in the group response with IGMP Report 6. If multiple routers on a LAN, the router with lowest IP Address is elected as IGMP querier.

http://wiki.nil.com/AS-path_prepending_(technical_details ) http://ciscodreamer.blogspot.com/2009/07/bgp-as-path-prepending.html

Local Preference Attribute The local preference attribute is used to prefer an exit point from the local autonomous system (AS). Unlike the weight attribute, the local preference attribute is propagated throughout the local AS. If there are multiple exit points from the AS, the local preference attribute is used to select the exit point for a specific route. The default value for local preference is 100. with default local preference, let's take a look the output from R3, we can see R3 recevies the route of 192.168.12.0/24 from two paths, the interesting thing is that the path from 172.16.13.1 which is R1 has no Local Preference value displayed, the route from R4 (4.4.4.4) does have default Local Preference value 100. But when take a look closer, we can see both path have default value 100. R3>sh ip bgp 192.168.12.0/24 BGP routing table entry for 192.168.12.0/24, version 19 Paths: (2 available, best #2, table Default-IP-Routing-Table, not advertised to EBGP peer) Advertised to

The BGP local-as command has several keywords, this test is trying to clarify how to use them. According to Cisco documentation, this command is to support Dual AS configuration for network AS migration. Here we are assuming R2 is ISP and is planing to migrate from AS 200 to AS 2000. R3 is R2's customer, R1 is another ISP where we will check and verify if R2 AS# migration causes problem. 1. local-as without any other keywords. R2#sh run s bgp router bgp 200 no synchronization bgp log-neighbor-changes neighbor 10.10.12.1 remote-as 100 neighbor 10.10.23.3 remote-as 300 neighbor 10.10.23.3 local-as 2000 no auto-summary R2# hmm, got error: *Mar 1 02:24:26.247: %BGP-3-NOTIFICATION: received from neighbor 10.10.23.3 2/2 (peer in wrong AS) 2 bytes 07D0 looks R2 is using the local-AS command AS# instead of the bgp process AS# to talk to peer R3. Let's change R3 to use remote-as# 2000 for now. R3#sh run s bgp router bgp 300 no synchronization bgp log-neighbor-changes network 192.168.10.

Server A and Server B are in different VLANs on the CSS, if interfaces and circuit VLANs are configured properly, then Server A needs to talk to Server B or vice versa, what other configuration is needed on CSS? do we need VIP and Soruce Group? The answer is: the CSS by default routes traffic between VLANs, so no VIP or Group configuration is needed.

iBGP is running between routers in same sub-AS, eBGP is running between different sub-AS. However, when BGP calculate bset path, it doesn't treat them as real iBGP and eBGP R4 received route to 200.200.200.8/29 which is in AS 200 from both AS100 eBGP router and iBGP router in sub AS64526. Path going through AS100 seems a shorter, but according to Cisco documentation, confederation AS_CONFED_SEQUENCE doesn't take account when BGP select best path. http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml we can see R4 choose internal router R5 as the best path to 200.200.200.8/29 What the relationship between R2 and R4, they are both RR for redundancy. The IPExpert video configured them as RR-Client to each other, is this correct or doesn't matter? searched Internet seems most example they are just regular iBGP peers. If they configured as RR-client to each other, when R4 received a route 200.200.200.32/28 from AS 100, it sent to R2, since R2 des

Have been a networker for years, didn't take any action to pursue a CCIE certificate until recently, one reason is that I think CCIE doesn't mean everything for a networker. Be a good networker , we definitely need more knowledge than Cisco stuff and more experiences of dealing with real world chanllenges. I changed my mind and on the jounrney of CCIE R&S now. Time is an issue to me as I have a busy work and a 17 months old little girl at home. Plan to take my first try at the end of 2010. I have IPExpert selfstudy materials and some PDF books. I know I will be really busy for at least half year. :) Jason