how many questions are on ccna exam

how many questions are on ccna exam

The IS-IS packets have the same common 8B above , and the additional header fields are different, and then the TLV field. At the time of packet capture , the ternary in the TLV : type, length, variable length content, type and length in the packet, the packet capture software may not be presented, but the type and length can be found from the binary code of the packet capture result. content. Device Configuration Mpls traffic-eng tunnels ip rsvp bandwidth Network 10.1.23.3 0.0.0.0 area 0 Local *Aug 18 11:26:02.546: Ip explicit R1toR5 It became untagged , before it was POP , why is it untagged now? Analysis, we modified the R2 's loopback mouth, into 2.2.2.2/24 , then for R2 own, this is the direct route 2.2.2.0/24 , right? R2 may for this 2.2.2.0/24 assign a label, since it is directly connected, so R2 to this prefix divided empty tag 3 . Then send the label mapping message to other LDP neighbors including R1 and R3 : Both are link state routing protocols, which require routers in the area to exchange link state information, and link state information is collected in the link state database. Router ospf 1 Assign and distribute labels Peer LDP Ident: 4.4.4.4:0; Local LDP Ident 2.2.2.2:0 TCP connection: 4.4.4.4.24940 - 2.2.2.2.646 The POP will only pop the top label header. The packet forwarded by this action can be an IP packet or an MPLS label packet. ! Route summary divides the original segment of LSP into two segments 10.1.24.0 [115/20] via 10.1.123.2, FastEthernet0/0 Priority 1 : 9375000 204 ID: path option 10 [1] Mpls traffic-eng router-id Loopback0 mpls traffic-eng area 0 Then from the tunnel0 port, cost=1+1=2 , better, so the routing table of R2 changes: Next-address 10.1.24.4 LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL Configured Areas: 1 Inter-domain routing protocol Link attribute Network 10.1.12.2 0.0.0.0 area 0 Fast Reroute PATH IS-IS area AutoBandwidth Router ospf 1 mpls ldp sync Router ospf 100 Interface eth 0/0 IGP System ID: 2.2.2.2 LSPID Tunnel mpls traffic-eng bandwidth 33000 Src 2.2.2.2, Dst 4.4.4.4, Tun_Id 0, Tun_Instance 6 RSVP Path Info: Bytes tag Interface eth 0/0 Version=0, length in words=7 Explicit Route: 10.1.23.3 10.1.34.3 10.1.34.4 4.4.4.4 55000 Like all IS-IS packets, the HELLO package consists of a header and a TLV . *Aug 18 09:06:07.919: Path Latency (microseconds):0 Pop tag Router-id 4.4.4.4 Network 10.1.34.4 0.0.0.0 area 0 Path Protect Parameters: MPLS VPN configuration Mpls traffic-eng tunnels mpls label range 300 399 Note that since R1 activates MPLS LDP-IGP synchronization, before the LDP adjacency relationship between R1 and R4 is established, the interface connecting R4 on R1 will not send OSPF HELLO packets, that is, R1-R4 . OSPF adjacencies can never be established. Of course, we don't want to watch the R1-R4 screw up, it's not good for anyone, isn't it? So configure one on R1 : This can be area at any level within the router adjacency relationship; may be other area adjacent L2 or L1 / L2 router forming L2 The interval at which the DIS sends CSNP packets is 10S by default. !! Activate IS-IS on the interface 0x26DC *Aug 18 09:06:07.919: LABEL_REQUEST type 1 length 8 : Tunnel mpls traffic-eng bandwidth 2000 R1#show mpls traffic-eng tunnels Ip cef If the PSNP acknowledgment is still not received after the retransmission timout , the originating router will retransmit the LSP. IS-IS Level-1 LSP R1.00-00 Tunnel mpls traffic-eng path-option 10 explicit name R1toR5 Additional Knowledge: Label-to-label TTL diffusion behavior in SWAP , PUSH , POP operations 75000 Reservable Bandwidth[5]: R1(config)#ip route 4.4.4.4 255.255.255.255 tunnel 0 R1#show ip route 202 Fa0/0 Mpls ldp router-id loopback0 mpls label range 400 499 interface fast0/0 IS-IS Adjacency related packets debugging is on R1# Do not need to explain it again? At R4 , R4 pops the top label and forwards the packet to R5. Tspec: ave rate=20000 kbits, burst=1000 bytes, peak rate=20000 kbits RSVP Resv Info: 10.1.45.0/24 R1(config-keychain-key)#key-string cisco R1(config-keychain-key)#exit Comprising one or more routers is configured on the source IP address, the CISCO IOS in In R2 configuration backup link, R2 increase in the following configuration: Outgoing tag or VC Here there is a potential problem, because Level1 Router , do not know level2 routing (outside the region) information, instead of looking for the nearest L1 / L2 router to your destination, then it may appear sub-optimal path In order to solve this problem, IS-IS introduced a mechanism called route leakage. *Aug 18 09:06:07.919: version=0, length in words=7 55.55.55.55 [110/31] via 10.1.23.3, 00:02:29, Ethernet0/1 Network 10.1.34.4 0.0.0.0 area 0 Interface is up and sending maximum metric *Aug 18 09:06:02.699: Minimum Path Bandwidth (bytes/sec): 1250000 75000 R3.02-00 Set-overload-bit on-startup <5-86400 sencondes> Nexthop 10.1.12.2 FastEthernet0/0 label 204 MPLS LDP-IGP synchronization is enabled in the IGP process and applied to all interfaces running the IGP . Basic experiment Oper: up And in R2 , the label package is pushed into a new layer of labels, the outer label is assigned by R3 , and the inner label is assigned by R4 . Manually reoptimize 75000 kbits/sec, MPLS is a CISCO proprietary protocol, later IETF borrowed, in IETF is called Tag Switching , can be understood as both a different name when enabled, the protocol used is not the same 104 0xA538 R2 redistributed direct route 2.2.2.0 is gone, inter-area route is still,how many questions are on ccna exam, and R1 no longer uses R2 as the next hop of the default route. Note that the LSP sent by R2 is also overload-bit set. . Network 10.1.12.1 0.0.0.0 area 0 Outgoing Regional prefix replacement. As shown above, you want to replace the original area prefix 49.0001 with 49.0002 . To achieve this goal, configure an NSAP address for the new area prefix on A and B. Note that the SystemIDs of the two addresses must be the same. Then delete the areas of A and B in turn . Attribute Flags: 0x00000000 Interface eth 0/0 Generate a default route to this device as the egress route by ATT bit with its nearest L1/L2 router *Mar 1 00:00:32.755: ISIS-Upd: Building L1 LSP Basic architecture *Aug 18 09:06:07.919: Setup Prio: 7, Holding Prio: 7 Interface eth 0/0 After the tunnel setup failed There are actually some hidden dangers here. For example, using traceroute may expose the internal structure of the network ( after TTL=0 , the router will return an error message, which may expose network information). Explicit empty label Equivalent load balancing in CEF ! Router bgp 2345 Three-Way Handshake for IS-IS Point-to-Point Adjacencies 1.1.1.1:0 Attribute tag and affinity attribute R3#sh mpls forwarding-table Find a LFIB , LFIB has the next hop information, so the top label is popped up and then handed over to the next hop without having to look up the FIB table again (if the label is popped, it is an IP packet). Bytes tag switched This inbound label packet, with a label value of 203 , indicates in the LFIB table of R2 that 203 needs to be exchanged to 300 and then dropped to the next hop. Route summary divides the original segment of LSP into two segments Next-address 10.1.34.4 Interface Serial0/0 MPLS VPN Architecture CCSP Edition MPLS TE router ID: 1.1.1.1 Is an extended form of type 2 TLV Router ospf 1 Mpls traffic-eng tunnels ip rsvp bandwidth Net 49.0001.0000.0000.0002.00 Delay metric is optional, the link transmission delay is not supported. Recommendations for Interoperable IP Networks using IS-IS Integrated IS-IS and OSPF are 20 century 80 late-defined, which is about 1988 years. OSPF actually evolved from an earlier version of IS-IS , but it uses IP as a precondition. The core concepts of OSPF , such as the proliferation of link state information, the SPF algorithm, and the use of designated routers in the broadcast link, are borrowed from the IS-IS early version. Both use a similar mechanism for routing information exchange, namely diffusion By default, the cost of an OSPF interface is calculated based on the bandwidth. *Aug 18 09:06:07.919: Ip cef Down Thresholds: 100 99 98 97 96 95 90 85 80 75 60 45 30 15 The IS-IS packets have the same common 8B above , and the additional header fields are different, and then the TLV field. At the time of packet capture , the ternary in the TLV : type, length, variable length content, type and length in the packet, the packet capture software may not be presented, but the type and length can be found from the binary code of the packet capture result. content. *Aug 18 09:06:07.919: 10.1.12.1 (Strict IPv4 Prefix, 8 bytes, /32) *Aug 18 09:06:07.919: 10.1.12.2 (Strict IPv4 Prefix, 8 bytes, /32) The command to define an Explicit path is as follows: Prefix RFC1195 0x00000029 (Tunnel0) Destination: 5.5.5.5 Keep priority Basic experiment Section LAN ID as 1921.6811.1001. 03 . " the routers connected to the multiaccess network (Ethernet) all have the same circuit ID . The circuit ID is a one-octet number that the router uses to uniquely identify the By default, IS-IS of the LSP maximum survival time of 1200s , To add: In the above environment, the loopback interface cost=1 , and the cost of all other physical interfaces =10 . Then if we configure: In a typical network design, multiple independent Level1 areas are connected through a backbone network, and the backbone network is composed of routers with Level 2 routing functions. The Level1-2 router has two independent link state databases that support Level1 and Level2 routing , respectively . The PATH message carries a label request object, which is hopped and hopped from the tunnel first-end router to the tail router. Router ospf 1 Point2point LDP discovery sources: Basic ( NLPID 0x81 ) and IP ( 0xCC ) Interface fas0/0 Interface eth 0/0 CSPF algorithm overview OSP PDU 1.1.1.1:0 Imagine if AB link between carrying a lot of the Tunnel , then when this root link DOWN out of time, will likely trigger a large amount in a short time PATHtear and ResvTear , so how to optimize it? 103 !! Specify the range of local tags, this can be a great convenience in the experiment Network 2.2.2.2 0.0.0.0 area 0 !! Bandwidth requirement is 20M LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL The PATH message carries a label request object, which is hopped and hopped from the tunnel first-end router to the tail router. ! Label Global Pool BW Unreserved: LSPID Configuration example 2 : 10.1.23.2 A new LSP is triggered immediately and the ATT is not set. As a result, R1 revokes the default route that originally pointed to R2 . Mpls traffic-eng router-id loopback0 mpls traffic-eng area 0 Global Pool Sub Pool TOS 0 Metrics: 1000 !! default tunnel port advertised cost = 1000 Mpls traffic-eng tunnels mpls label range 200 299 10.1.23.3 [MPLS: Labels 300/403 Exp 0] 0 msec 4 msec 0 msec Solution: Establish a targeted LDP neighbor relationship between R2 and R4 Type 1 length 12: Configure this hidden command on the penultimate hop router (that is, R2 in the figure above ): Network Next Hop In label/Out label 10.1.12.2 SRM : used to control the delivery of LSPs to adjacent routers during the update process. Frame-relay map ip 10.1.123.3 201 broadcast frame-relay map clns 201 broadcast Router-id 1.1.1.1 R2-PE1#show mpls traffic-eng tunnels Interface eth 0/1 Area Address: 49.0001 6bits LDP allows non-directly connected neighbors, so that neighbors discover that they do not need to rely on multicast HELLO packets, but instead use unicast packets. 4 is IPv4 . If it is 6 or IPv6 , the LSR uses this value to determine whether the message is V4 or V6 , and then selects a complex equalization algorithm according to different IP versions. How labels are handled Use the clns host command in global configuration mode to establish a mapping of hostnames to NSAP addresses. In this way, in the link state database, LSP Now the initial environment, R1 can learn inter-area routes, and R2 locally re - routes to level 1 route 2.2.2.0 . Of course, since R2 sets the attached-bit , R1 also generates a default route to R2 . Net 49.0001.0000.0000.0002.00 Network 10.1.34.4 0.0.0.0 area 0 Support IP classless routing prefix (support VLSM ) TE tunnels are distinct from MPLS LSP through which it traverses: Opaque ID: 0 Next Hop 10.1.23.2 If the link or node fails, the traffic will be rerouted due to the failure. If the rerouting takes a few seconds, the high performance of the link will cause a large amount of traffic pointing to the fault point to be discarded. For some businesses, business interruption may result. *Aug 18 04:37:06.239: Error Node: 10.1.12.2 132 Otherwise, the interface may be considered in MPLS-LDP Discovery Transport interface address , the Transport Address configured as Direct interface IP address. Ip address 10.1.34.3 255.255.255.0 Tunnel mpls traffic-eng autoroute announce tunnel mpls traffic-eng priority 7 7 Tib entry: 1.1.1.1/32, rev 2 Mpls traffic-eng tunnels ip rsvp bandwidth R1#show mpls forwarding-table 4.4.4.0 detail Mpls traffic-eng reoptimize events link-up We found, R2 external routing re-released locally gone; R2 from level2 injection level1 of inter-area routes are gone; while R2 can not be used as R1 next hop of the default route. There is only one R2 local direct connection 24.0 route. 10.1.34.0/24 Interface loopback0 Fspec: ave rate=20000 kbits, burst=1000 bytes, peak rate=20000 kbits History: Mpls ip interface fast1/0 First we look at R1 : LSP packet structure R2(config)#key chain test R2 (config-keychain)#key 1 Link State ID: 2.2.2.2 Advertising Router: 2.2.2.2 LS Seq Number: 80000011 Checksum: 0xAE93 Length: 72 The tunnel 's build priority cannot be set higher than the hold priority. i L2 2.2.2.0 [115/20] via 10.1.24.2, Serial0/0 Contains the tunnel's prioritization, hold priority, and some flags Mpls traffic-eng tunnels ip rsvp bandwidth 0 kbits/sec Mpls ldp router-id Loopback0 *Aug 18 09:06:07.919: version:1 flags:0000 cksum:0000 ttl:255 reserved:0 length:232 ! The interface of each router activates RSVP and MPLS TE tunnel support. 75000 kbits/sec, Lists the Layer 3 protocol supported by the integrated IS-IS protocol. Currently only CLNP Going f.0/0 , the outbound tag used is 200 , while 10.1.35.5 accesses 1.1.1.1 and goes to F1/0 , and the outbound tag used is 400 . Outgoing Label The CSPF calculation is performed by the head end of the tunnel , and the result of the calculation is a string of IP ( path of the tunnel ) Reservable Global Pool BW: 75000 kbits/sec Reservable Bandwidth[7]: Interface fast 1/0 Destination-based load balancing is actually achieved by HASHing the destination and source IP addresses . In other words, it is actually based on source and destination address pairs for load balancing. The configuration of R5 is supplemented as follows: IS-IS of IIH will be marked with a lot of padding , the Hello packets filled out the interface MTU . This mechanism will be more vulnerable on low-bandwidth links. You can cancel padding on the interface with no isis hello padding . This command, if you want to play, is recommended to be added at both ends of the link. The result of the experimental pro-test is that if no one drops hello padding , the adjacency can still be established.