Lab 19(b)2. L3 Switch Routed Ports

Transcription

1 Lab 9(b). L Switch Routed Ports Rev c cnac o okbook.com G O A L onfigure a routed port on to communicate with R. Topology For simplicity, you can reuse the physical topology of the previous labs, 9a and 9(b). onceptually, we'll begin looking at this as a hub and spoke network, where our VLANs are access layer (as opposed to distribution or backbone) spokes, and lead only to end devices. The "rest of the world" will be in the direction of the router, R. This has two effects: The IP subnets associated with our VLANs are stub networks that will never lead to routers and other networks. They are directly connected to and automatically appear in its routing table. Because the connection from to the rest of the world is L, those VLANs and their subnets are done. They won't reappear on other switches on the other side of R because that would create discontiguous subnets and unreliable routing. Technically, the VLAN numbers 0 and 0 could be reused for different VLANs and subnets on the other side of R without finding out, since VTP and DTP aren't routed protocols. In fact someone, somewhere on the internet surely is, but that would be monumentally bad practice if it happened within the same company. This sets up the perfect use case for a default route on pointing to R and a single summary route on R pointing to. O N F I G U R A T I O N S T E P S Make your starting configuration match the ending configuration of the previous lab, 9(b). The hosts will be configured with IP addresses and default gateways The host switchports will be in the appropriate VLANs SVIs provide default gateways for each VLAN L routing between the VLANs is enabled on the switch and the hosts can ping each other. It should resemble the configuration on the right. Gi 0/ /0 Fa 0/ /0 Fa 0/ VLAN 0 Fa 0/ VLAN 0 Starting onfiguration H Address: / Gateway: H Address: / Gateway: hostname no ip domain-lookup line con 0 exec-timeout 0 0 logging synchronous interface FastEthernet0/ switchport access vlan 0 switchport mode access interface FastEthernet0/ switchport access vlan 0 switchport mode access interface FastEthernet0/ shutdown interface Vlan0 ip address interface Vlan0 ip address ip routing NA (00-0) LAB 9(B) L SWITH ROUTED PORTS 00- BEN STEEL L9(b) -

2 onfigure the router-facing port on as a routed L interface with an IP address of /. onfigure the switch-facing interface on R with the IP address /. Use a single route on to reach R any future networks that may be added beyond R. Use a single route on R to reach all subnets currently connected to, without including any unused subnets that are not mathematically necessary. Make sure the ports that connect the router and switch are not shutdown and test by inspecting 's routing table and pinging the R address from one of the hosts. V E R I F I A T I O N What route did you need to add to 's routing table? What route did you need to add to R's routing table? What range of IP addresses is covered by the summary Route on R If you were allowed two summary routes on R to create a single contiguous block of addresses with minimal spillover, what would they be? What range of IP addresses would that cover? L9(b) BEN STEEL LAB 9(B) L SWITH ROUTED PORTS NA (00-0)

3 O N F I G U R A T I O N W A L K T H R O U G H Verify That the onfiguration from Lab 9(b) is Working 9 0 # show interfaces status Port Name Status Vlan Duplex Speed Type Fa0/ connected 0 a-full a-00 0/00BaseTX Fa0/ connected 0 a-full a-00 0/00BaseTX Fa0/ Trunk to R disabled auto auto 0/00BaseTX # show ip interf brief Interface IP-Address OK? Method Status Protocol Vlan unassigned YES NVRAM administratively down down Vlan YES manual up up Vlan YES manual up up FastEthernet0/ unassigned YES unset up up FastEthernet0/ unassigned YES unset up up FastEthernet0/ unassigned YES unset administratively down down On your switch, make sure that your access interfaces are in the right VLANs [Lines -] and not shutdown [Lines - and -], your SVIs are configured [Lines -], that L IP routing is turned on, and that the link to the router is down [Line ], guaranteeing that any routing is happening on the switch. On one of your hosts, try pinging the other. H H> ping Sending, 00-byte IMP Echos to , timeout is seconds: Success rate is 00 percent (/), round-trip min/avg/max = // ms onfigure a Layer Routed Link Between and R Back to your switch, configure the router-facing port on as a routed L interface and give it an IP address of /. (config)# interf fa0/ (config-if)# no switchport (config-if)# ip address (config-if)# no shut I like to think of processes running on interfaces. From that viewpoint, we first turn off the process that was handling L switching on our interface [line ] and start a process to handle L routing through the interface [line ] Now, we can clean up the router interface's configuration (if needed) and add a fresh IP address in the same subnet. NA (00-0) LAB 9(B) L SWITH ROUTED PORTS 00- BEN STEEL L9(b) -

4 R R# show ip interf br Interface IP-Address OK? Method Status Protocol GigabitEthernet0/0 unassigned YES manual up up GigabitEthernet0/ YES NVRAM up up GigabitEthernet0/ YES NVRAM up up We still have some old subinterfaces from previous labs. R# conf t R(config)# no interf gi0/0.0 R(config)# no interf gi0/0.0 That should get rid of them. R(config)# interf gi0/0 R(config-if)# description TO R(config-if)# ip address R(config-if)# no shutdown R(config-if)# end R# show ip interf br Interface IP-Address OK? Method Status Protocol GigabitEthernet0/ YES manual up up GigabitEthernet0/0.0 unassigned YES manual deleted down GigabitEthernet0/0.0 unassigned YES manual deleted down The "deleted" subinterfaces [Lines -] are curious but harmless. If you look in the runningconfig, they're not there. Now we can test the L link from both the switch and one of the hosts # ping Sending, 00-byte IMP Echos to 0..0., timeout is seconds:. Success rate is 0 percent (/), round-trip min/avg/max = // ms H H> ping Sending, 00-byte IMP Echos to 0..0., timeout is seconds:... Success rate is 0 percent (0/) The ping from the host to the router failed and a check of our routing tables shows why # show ip route Route source code legend omitted Gateway of last resort is not set / is variably subnetted, subnets, masks / is directly connected, Vlan /0 is directly connected, FastEthernet0/ / is directly connected, Vlan0 Switch, our host's default gateway, knows how to get to on the router [line ]. L9(b) BEN STEEL LAB 9(B) L SWITH ROUTED PORTS NA (00-0)

5 R R# show ip route Route source code legend omitted Gateway of last resort is not set L / is variably subnetted, subnets, masks /0 is directly connected, GigabitEthernet0/ / is directly connected, GigabitEthernet0/0 But the router doesn't know how to get its reply back to the source ping's source. It has no route to H's subnet ( /) and has no default route [Line ] To make this one ping work, we could just add a route on R, but we'll fix it more fully by finishing the objectives of the lab Add a default route from to R Add a summary route on R to, covering all the subnets currently in use on (config)# ip route fa0/ R R(config)# ip route gi0/ The default route was easy and didn't really change anything because all of the routes in that direction are directly connected to the switch and already in its routing table. The summary route on R fixes our ping problem and will send all packets destined to the addresses through 0... toward forevermore. Our ping from H to the router now works. R E A P A N D V E R I F I A T I O N To use an interface on a multilayer switch (L switch), turn off its L switching and give it an IP address. (config-if)# no switchport (config-if)# ip address To verify that the port is now an L routed port, don't rely on the "show interfaces" command. On a router, that command will mention an IP address, but might not on a switch. In fact on the switch I'm using, the output doesn't change at all from when it was a switchport. The "show ip interface" command can be very different between L switchports and L routed ports. #show ip interf fa0/ FastEthernet0/ is up, line protocol is up Inbound access list is not set That's it for a switchport #show ip interf fa0/ FastEthernet0/ is up, line protocol is up Internet address is 0..0./0 Broadcast address is... Address determined by setup command more lines for a layer routed port NA (00-0) LAB 9(B) L SWITH ROUTED PORTS 00- BEN STEEL L9(b) -