Two networks, one connection
Connect a Cisco branch to a Huawei branch. Interfaces and hosts are ready; add a static route in each direction to deliver the first ping.
Connect a Cisco branch to a Huawei branch. Interfaces and hosts are ready; add a static route in each direction to deliver the first ping.
Build single-area OSPF between three routers. Then adjust interface costs to choose between the direct path and the path through R3. This is a simplified routing exercise.
PC1 and PC2 share VLAN 10 on different switches. Move the host ports into VLAN 10 and configure a trunk between Cisco and Huawei. SW2 starts with its host port in VLAN 20, so connectivity is broken.
Configure the XR branch using a candidate configuration. Verify that nothing changes until commit, then route to the Huawei branch.
Build directly connected IPv4 eBGP between Cisco AS 65001 and Huawei AS 65002. Advertise each branch LAN, then check the AS path.
Exchange branch prefixes between IOS XR and Huawei. Apply an explicit pass policy in both directions on XR, then commit.
Both branch routers run Huawei VRP-style CLI. Configure static routes using system-view and verify two-way reachability.
Routing already works. Create an ICMP deny policy on R1, observe the failed ping, then remove the binding and restore reachability.
Harden R1 the Cisco way: hostname, enable secret, console and VTY passwords, a banner and SSH with local users. Save when done.
PC1 (VLAN 10) and PC2 (VLAN 20) share one switch. Route between the VLANs with 802.1Q subinterfaces on R1 over a single trunk. R1 G0/0 starts shut down.
Route between VLAN 10 and VLAN 20 inside the switch using switched virtual interfaces. Cisco switches route only after ip routing.
Three switches form a loop. Spanning tree blocks one port. Choose the root bridge deliberately, run the rapid protocol and mark host ports as edge ports.
Two parallel links join SW1 and SW2. Bundle them with LACP so both links forward, then carry VLAN 10 across the bundle as a trunk.
R1 serves addresses for both LANs. PC2 sits behind R2, so R2 must relay its broadcast to R1. Routing between the routers is already in place.
The ISP has no route back to 192.168.10.0/24. Give R1 a default route and translate the inside hosts to its public address so replies return.
PC1 uses 192.168.10.1 as its gateway, but no router owns that address yet. R1 and R2 share it as a virtual IP. R1 is preferred; when its uplink fails, R2 takes over. OSPF already runs on all three routers.
LAN B (192.168.20.0/24) must not reach the server; LAN A still must. A standard ACL only matches the source, so apply it close to the destination: outbound on the server interface.
Four routers share one Ethernet segment, so OSPF elects a designated router (DR) and a backup (BDR). Router IDs 1.1.1.1–4.4.4.4 make R4 the default DR. Use interface priorities to choose your own.
R1 sits in area 1, R3 in the backbone, and R2 is the area border router. Build the areas, then summarize area 1’s 172.16.x networks at the ABR.
Three Cisco routers form a triangle. Run EIGRP, slow down the direct R1–R3 link and find the successor and the loop-free backup (feasible successor) R1 keeps for 192.168.3.0/24. EIGRP is Cisco-proprietary; Huawei VRP does not run it.
R1 runs EIGRP, R3 runs OSPF, and R2 runs both. Redistribute in both directions on R2 so each side learns the other as external routes.
R1 (AS 65001) peers with R2 over eBGP. R2 and R3 (AS 65002) form iBGP between loopbacks; OSPF inside AS 65002 already carries the loopbacks. R3 will learn R1’s network with an unreachable next hop until R2 changes it.
R1 (AS 65001) is dual-homed to ISP-A (R2, AS 65002) and ISP-B (R3, AS 65003). Both reach 8.8.8.0/24 in AS 65004. Send outbound traffic via ISP-B with local preference, and pull inbound traffic to ISP-A by prepending your AS toward ISP-B.
PC1 uses 192.168.10.1 as its gateway, but no router owns that address yet. R1 and R2 share it as a virtual IP. R1 is preferred; when its uplink fails, R2 takes over. OSPF already runs on all three routers.
OSPF is configured on all three routers, but PC1 cannot reach PC2. Three configuration faults stop the adjacencies. Find them with the neighbor and interface show commands; the RouteCraft diagnostic lines point at mismatches.
Harden R1 the Huawei way: system name, console password, AAA users, SSH-only VTY access and a login header. Save when done.
PC1 (VLAN 10) and PC2 (VLAN 20) share one switch. Route between the VLANs with 802.1Q subinterfaces on R1 over a single trunk. Huawei dot1q termination subinterfaces also need arp broadcast enable.
Route between VLAN 10 and VLAN 20 inside the switch using VLANIF interfaces. Huawei switches route between VLANIFs by default.
Three switches form a loop. Spanning tree blocks one port. Choose the root bridge deliberately, run the rapid protocol and mark host ports as edge ports.
Two parallel links join SW1 and SW2. Bundle them with LACP so both links forward, then carry VLAN 10 across the bundle as a trunk.
R1 serves addresses for both LANs. PC2 sits behind R2, so R2 must relay its broadcast to R1. Routing between the routers is already in place.
The ISP has no route back to 192.168.10.0/24. Give R1 a default route and translate the inside hosts to its public address so replies return.
PC1 uses 192.168.10.1 as its gateway, but no router owns that address yet. R1 and R2 share it as a virtual IP. R1 is preferred; when its uplink fails, R2 takes over. OSPF already runs on all three routers.
LAN B (192.168.20.0/24) must not reach the server; LAN A still must. A basic ACL only matches the source, so apply it close to the destination: outbound on the server interface.
Three Huawei routers in a chain. Run RIP version 2, advertise the classful networks, disable summarization and keep updates off the host LANs.
Build OSPF area 0 across three Huawei routers with fixed router IDs, keep the host LAN silent, and let edge router R3 advertise a default route toward the ISP.
Four routers share one Ethernet segment, so OSPF elects a designated router (DR) and a backup (BDR). Router IDs 1.1.1.1–4.4.4.4 make R4 the default DR. Use interface priorities to choose your own.
R1 sits in area 1, R3 in the backbone, and R2 is the area border router. Build the areas, then summarize area 1’s 172.16.x networks at the ABR and turn area 1 into a totally stubby area.
R1 runs RIP, R3 runs OSPF and R2 runs both. Use import-route on R2 in both directions so each domain learns the other.
R1 (AS 65001) peers with R2 over eBGP. R2 and R3 (AS 65002) form iBGP between loopbacks; OSPF inside AS 65002 already carries the loopbacks. R3 will learn R1’s network with an unreachable next hop until R2 changes it.
R1 (AS 65001) is dual-homed to ISP-A (R2, AS 65002) and ISP-B (R3, AS 65003). Both reach 8.8.8.0/24 in AS 65004. Send outbound traffic via ISP-B with local preference, and pull inbound traffic to ISP-A by prepending your AS toward ISP-B.
Two parallel links join SW1 and SW2. Bundle them with LACP so both links forward, then carry VLAN 10 across the bundle as a trunk. LACP is a standard, so a Cisco port-channel and a Huawei Eth-Trunk interoperate.
PC1 uses 192.168.10.1 as its gateway, but no router owns that address yet. R1 and R2 share it as a virtual IP. R1 is preferred; when its uplink fails, R2 takes over. VRRP is a standard, so Cisco and Huawei routers can form one group. OSPF already runs on all three routers.
R1 runs EIGRP, R3 runs OSPF on Huawei VRP (which has no EIGRP), and R2 runs both. Redistribute in both directions on R2 so each side learns the other as external routes.
R1 (AS 65001) peers with R2 over eBGP. R2 and R3 (AS 65002) form iBGP between loopbacks; OSPF inside AS 65002 already carries the loopbacks. R3 will learn R1’s network with an unreachable next hop until R2 changes it.
OSPF is configured on all three routers, but PC1 cannot reach PC2. Three configuration faults stop the adjacencies. Find them with the neighbor and interface show commands; the RouteCraft diagnostic lines point at mismatches.
A Cisco access switch, a Huawei core switch that routes and hands out addresses, a Cisco edge router with PAT, and a Huawei ISP. Build every layer so both VLANs get DHCP leases and reach 8.8.8.8.
Bring IPv6 up between two branches. Address both routers, fix a link-local address for a clean next hop, add static routes both ways, and let PC1 configure itself from router advertisements (SLAAC).
Bring IPv6 up between two branches. Address both routers, fix a link-local address for a clean next hop, add static routes both ways, and let PC1 configure itself from router advertisements (SLAAC).
IPv6 addressing is in place; the routers have no IPv4 at all. Run OSPFv3 with area 0 between R1 and R2 and area 1 between R2 and R3. Neighbors form over link-local addresses, and the router ID still has to be a 32-bit value.
IPv6 addressing is in place; the routers have no IPv4 at all. Run OSPFv3 with area 0 between R1 and R2 and area 1 between R2 and R3. Neighbors form over link-local addresses, and the router ID still has to be a 32-bit value.
IPv4 and OSPFv2 already run across Cisco R1, Huawei R2 and Cisco R3. Add IPv6 next to it and run OSPFv3 across both vendors. The Cisco routers borrow their IPv4 router ID; Huawei needs one configured.
Service providers run IS-IS in the core. Give three routers a NET, run them as one Level-2 backbone, advertise each router’s loopback, and confirm R1 learns R3’s loopback through IS-IS.
IS-IS already connects PE1, P and PE2. Turn the core into an MPLS network: give each router an LDP identity, enable LDP on the core links, check the sessions and labels, and follow the label-switched path from PE1 to PE2’s loopback.
A customer in AS 65100 connects to your PE in AS 65000. Bring up eBGP, send the customer your Internet prefix, and accept only the customer’s own /24, even though the CE also advertises a private 10.99.0.0/16 by mistake.
Build a two-area IS-IS design. R1 is a Level-1 router in area 49.0001, R2 is the Level-1-2 border of that area, and R3 sits in the Level-2 backbone in area 49.0002. R1 never learns the backbone’s routes: it follows the default route that R2’s ATT bit creates.
Three PEs hang off one core router, and IS-IS already carries the loopbacks. Instead of a full iBGP mesh, every PE peers only with the route reflector, and the RR reflects each customer prefix to the other PEs with the original next hop.
The provider core already runs IS-IS and LDP. Connect customer A’s two sites through it: create the VRF on both PEs, attach the CE links, carry the customer routes in MP-BGP VPNv4 between the PE loopbacks, and prove the P router never sees a customer route.
Customer A’s VPN was handed over “finished”, but CE1 cannot reach 192.168.2.1. Three faults are hidden in the core and on PE2. Use the VPN, BGP and MPLS show commands to find each one, fix it, and prove the service works.
Build a two-area IS-IS design. R1 is a Level-1 router in area 49.0001, R2 is the Level-1-2 border of that area, and R3 sits in the Level-2 backbone in area 49.0002. R1 never learns the backbone’s routes: it follows the default route that R2’s ATT bit creates.
IS-IS already connects PE1, P and PE2. Turn the core into an MPLS network: give each router an LDP identity, enable LDP on the core links, check the sessions and labels, and follow the label-switched path from PE1 to PE2’s loopback.
Three PEs hang off one core router, and IS-IS already carries the loopbacks. Instead of a full iBGP mesh, every PE peers only with the route reflector, and the RR reflects each customer prefix to the other PEs with the original next hop.
The provider core already runs IS-IS and LDP. Connect customer A’s two sites through it: create the VPN instance on both PEs, attach the CE links, carry the customer routes in MP-BGP VPNv4 between the PE loopbacks, and prove the P router never sees a customer route.
Customer A’s VPN was handed over “finished”, but CE1 cannot reach 192.168.2.1. Three faults are hidden in the core and on PE2. Use the VPN, BGP and MPLS show commands to find each one, fix it, and prove the service works.
The provider core already runs IS-IS and LDP. Connect customer A’s two sites through it: create the VRF on both PEs, attach the CE links, carry the customer routes in MP-BGP VPNv4 between the PE loopbacks, and prove the P router never sees a customer route. PE1 runs Cisco IOS and PE2 runs Huawei VRP: the RD and route targets must still match.
Two Nokia SR Linux leaves connect two host subnets over a /31 link. On SR Linux an address works only when its subinterface has IPv4 enabled and belongs to a network-instance. Set that up, add a static route each way with a next-hop group, and commit.
Two spines (AS 65000) and two leaves (AS 65101, 65102) run SR Linux, and every link is addressed and in network-instance default. Build the eBGP underlay. SR Linux rejects every eBGP route in and out until a policy allows it, so the policies are part of the job.
A Nokia SR Linux leaf (AS 65101) peers with an Arista leaf (AS 65102) over a /31. Both links and hosts are addressed. Bring up eBGP so each side learns the other host subnet. Arista accepts and advertises by default; SR Linux needs policies.
Two Nokia 7750 SR routers connect two LANs. SR OS ports start administratively down and nothing changes until you commit. Enable the ports, create the router interfaces, add a static route each way and commit.
Three SR OS routers in a chain are addressed, with system interfaces 1.1.1.1–3.3.3.3. The refreshed NRS I uses IS-IS rather than OSPF: run IS-IS instance 0 in area 49.0001 as Level 2, keep the system and LAN interfaces passive, and let PC1 reach PC2.
R1 (AS 65001) and R2 (AS 65002) are addressed. Bring up eBGP with a peer group, and advertise each LAN. On SR OS, BGP advertises nothing local until an export policy accepts it, so build a prefix list and a policy statement too.
PE1, P and PE2 already run IS-IS. Build label-switched paths between the PE system addresses: run LDP on every core interface, check the sessions, and find PE2’s system address in PE1’s tunnel table.
PE1 and PE3 hang off RR, and IS-IS carries all system addresses. Instead of a full mesh, every PE peers only with RR between system addresses, and RR reflects each customer LAN to the other PE with the original next hop.
The core already runs IS-IS and LDP. Connect customer A’s two sites with a VPRN service: iBGP VPN-IPv4 between the PEs, the service with its route distinguisher and route target, a SAP towards each CE, and a static route to each customer LAN. P never sees a customer route.
A Nokia 7750 SR and a Huawei router are addressed. Run IS-IS Level 2 in area 49.0001 between them, in each vendor’s own syntax, and let the LANs reach each other. Both derive nothing automatically except Nokia’s system ID.
Two OmniSwitches each have a host that belongs in VLAN 10. AOS has no configuration mode: you create the VLAN and assign ports to it with global vlan … members commands. The host ports are untagged members; the link between the switches is a tagged (802.1Q) member.
One OmniSwitch connects a host in VLAN 10 and a host in VLAN 20. On AOS you route between VLANs by binding a named IP interface to each VLAN; routing between IP interfaces is on by default.
Two OmniSwitches are joined over VLAN 100 and each has a host LAN. The VLANs and ports are already set. Give each switch its IP interfaces and add a static route in each direction.
Three OmniSwitches in a chain already have their VLANs and IP interfaces. Run OSPF area 0.0.0.0 on every IP interface so PC1 can reach PC2. On AOS the OSPF software must be loaded before it can be configured, and the protocol, the area binding and each interface are all enabled separately.
Two OmniSwitches are joined by two links (1/1/1 and 1/1/3). Bundle them into LACP link aggregate 1, so they act as one logical link, and carry VLAN 10 over the aggregate tagged. The host ports are already untagged in VLAN 10.
An OmniSwitch serves a campus LAN and hands off to a Cisco router over VLAN 100. The switch VLANs are already set. Address both sides and run OSPF area 0 so the two LANs learn about each other.
Two Arista switches each have a host. Put both host ports in VLAN 10 and carry it over an 802.1Q trunk between the switches. LEAF2 starts with its host port in VLAN 20, so the ping fails until you fix it.
One Arista switch connects a host in VLAN 10 and a host in VLAN 20. Route between them inside the switch with VLAN interfaces (SVIs). Like Cisco, EOS routes only after ip routing.
Two Arista switches act as routers between two LANs. Turn the links into routed ports, address them in prefix notation, and add a static route in each direction.
Three Arista switches are routed in a chain and already addressed. Run OSPF area 0 with fixed router IDs, keep the host LANs passive, and let OSPF find the far LAN.
A small leaf-spine fabric: two spines in AS 65000 and two leaves in AS 65101 and 65102. The point-to-point links are addressed. Build the eBGP underlay so each leaf learns the other leaf’s host subnet through both spines.
Two Arista distribution switches are joined by two links and share the users’ gateway. Bundle the links into a LACP port-channel that trunks VLAN 10, give each switch an SVI, and run VRRP so 192.168.10.1 stays up if one switch fails. DIST1 must be master.
An Arista data-center leaf (AS 65101) hands off to a Cisco WAN router (AS 65000). Address the link in each vendor’s own syntax, bring up eBGP, and exchange the two LANs. The router interfaces start shut down on the Cisco side.
SRC streams to group 239.1.1.1. OSPF is already running. Turn on multicast routing and PIM dense mode, let PC3 join the group, and watch dense mode flood the stream everywhere and then prune the branch toward R4, where nobody joined.
Sparse mode sends a stream only where it is requested. Make R2’s Loopback0 (2.2.2.2) the rendezvous point for every group, have PC3 and PC4 join 239.1.1.1, and follow the stream from the shared tree through the RP to the shortest-path tree.
Sparse mode is running, but no router knows an RP, so PC3’s join goes nowhere. Instead of typing the RP on every router, make R2 the bootstrap router (BSR) and R4’s Loopback0 the candidate RP. The BSR floods the RP to every PIM router.
With SSM there is no RP at all: the receiver names the source it wants, and its router joins that source directly. Enable SSM for 232.0.0.0/8, give PC3’s LAN IGMPv3 so it can name a source, and receive (10.1.1.10, 232.1.1.1).
Sparse mode with RP 2.2.2.2 is configured and PC3 and PC4 have joined 239.1.1.1, yet neither receives the stream. Use the RPF and PIM show commands to find the two faults and fix them.
Two PIM sparse-mode domains each keep their own RP: R2 (2.2.2.2) for domain A, where SRC sends, and R3 (3.3.3.3) for domain B, where PC4 has joined 239.1.1.1. RP-B never hears about SRC, so PC4 gets nothing. Peer the two RPs with MSDP so RP-A announces the source in a Source-Active message and RP-B joins it across the border.
RP-A (R2) and RP-B (R3) are configured as MSDP peers, but PC4 in domain B still receives nothing from SRC. Find out why the MSDP session stays down and fix it.
Three Huawei routers run OSPF. Turn on multicast, run PIM-DM on every routed interface, and enable IGMP on R3’s LAN so PC3 can join 239.1.1.1. Huawei runs IGMP only on interfaces where it is enabled, separately from PIM.
Run PIM sparse mode on three Huawei routers and use R2’s LoopBack0 (2.2.2.2) as the static RP, configured in the PIM view. PC3 joins 239.1.1.1 and SRC streams to it.
On VRP the range 232.0.0.0/8 is source-specific by default, so no RP is needed. Run PIM-SM, enable IGMPv3 on R3’s LAN, and let PC3 receive the channel (10.1.1.10, 232.1.1.1).
IOS XR turns on PIM and IGMP together: multicast-routing with interface all enable runs both on every interface. Add the static RP under router pim, commit, and stream 239.1.1.1 to PC3.
On IOS XR, 232.0.0.0/8 is SSM and IGMPv3 is the default, so enabling multicast is all it takes for a source-specific channel. No RP is configured.
Three Arista switches route with OSPF. On EOS multicast routing lives under router multicast, PIM is enabled per interface with pim ipv4 sparse-mode (which also enables IGMP), and the RP is set under router pim sparse-mode.
EOS answers IGMPv3 by default, but treats 232/8 as SSM only once you say so: ssm range standard under router pim sparse-mode. Build the channel (10.1.1.10, 232.1.1.1) without any RP.
Three 7750 SRs run OSPF. Add the router interfaces to PIM, set R2’s system address 2.2.2.2 as the static RP, and enable IGMP on R3’s LAN interface. SR OS runs IGMP only on interfaces listed under igmp.
SR OS treats 232.0.0.0/8 as SSM and speaks IGMPv3 by default. Add the interfaces to PIM, IGMP on R3’s LAN, and receive (10.1.1.10, 232.1.1.1) with no RP.
On SR Linux, PIM and IGMP are protocols of the network-instance, enabled per subinterface with admin-state enable. Make 2.2.2.2 (R2’s system0) the static rendezvous point.
SR Linux’s default SSM range is 232.0.0.0/8 and its IGMP default is version 3. Enable PIM and IGMP and receive the channel (10.1.1.10, 232.1.1.1) without an RP.
Three OmniSwitches route between VLAN IP interfaces with OSPF. On AOS, IGMP (IPMS) is switched on globally, PIM is loaded, each IP interface is added to PIM, and then dense mode is enabled.
Run PIM sparse mode on three OmniSwitches with SW2’s "to-sw1" address (10.0.12.2) as the static RP for 224.0.0.0/4.
R1 is a Cisco router (Loopback0 1.1.1.1), R2 a Huawei router and R3 an Arista switch, all running OSPF. Build one PIM sparse-mode domain with the Cisco loopback as the RP, each device in its own syntax.
A Nexus switch routes between two VLANs. NX-OS hides the SVI commands until feature interface-vlan is enabled, routing is always on (there is no ip routing), and addresses are written in prefix form.
Two Nexus switches are joined by a routed link (Ethernet1/1, 10.0.12.0/30); each has a routed LAN port on Ethernet1/2. Run OSPF the NX-OS way: there is no network statement, each interface joins the process itself.
N1 and N2 both carry VLAN 10 (SVIs 192.168.10.2 and .3 are configured). Give PC1 one gateway, 192.168.10.1, that survives the loss of either switch. NX-OS configures HSRP in its own sub-mode under the SVI.
Two Nexus switches are cabled with Ethernet1/3 and Ethernet1/4. Bundle both links into port-channel 10 with LACP and carry VLAN 10 over it as a trunk, so PC1 and PC2 (both in VLAN 10) can reach each other over both links.
NX-OS has no ip multicast-routing: feature pim turns multicast on. Run PIM sparse mode on both switches with N1’s Loopback0 (1.1.1.1) as the static RP, and stream 239.1.1.1 from SRC to PC3.
NX-OS treats 232.0.0.0/8 as SSM by default, so no RP is needed. The receiver joins a specific source, which needs IGMPv3 on its SVI-facing port (NX-OS defaults to IGMPv2).
SW3 already bundles its two uplinks into Port-channel10 with LACP, one to N1 and one to N2. Without vPC that bundle cannot form across two switches. Turn N1 and N2 into a vPC pair so SW3 sees one partner and forwards on both links.
The vPC domain is up: N1 is primary, N2 secondary, and SW3 forwards on both uplinks. PC3 hangs off N1 and PC2 off N2 on single, non-vPC ports. Break the peer-link and watch what each switch does while the keepalive is still alive.
The vPC domain is formed, but vPC 10 is only half working: SW3 bundles just one uplink, so all its traffic squeezes through N1. Find the mismatch with the consistency checker and fix it.
N1 and N2 have a vPC domain, a working peer-link and vPC 10, yet show vpc says the peer adjacency is not formed and SW3 bundles neither uplink. The keepalive is cabled on Ethernet1/8 and both ends have addresses. Find out why the peers cannot hear each other, and fix it without moving the cable.
The vPC domain is formed, but vPC 10 is suspended on N2 and SW3 bundles only its N1 uplink. Every per-vPC parameter matches. Look at the parameters the two peers must share for the whole domain.
The vPC pair works, but each peer is still its own spanning-tree bridge: whichever wins is the root, and if it fails SW3 has to elect a new one. With peer-switch both peers send the same bridge ID, so the pair itself is the root and losing a peer changes nothing for spanning tree.
N1 (192.168.10.2, 192.168.20.2) and N2 (.3) route between VLAN 10 and VLAN 20 with plain SVIs, no HSRP. PC1 uses N2’s own address 192.168.10.3 as its gateway. PC1 and PC4 sit behind the same vPC on SW3, yet PC1 cannot reach PC4 (192.168.20.40). Find out why, and fix it in the vPC domain.
Two data centers both use VLAN 10 (192.168.10.0/24), but they are joined only by a routed core. Extend VLAN 10 between them with OTV in unicast-only mode, so PCA reaches PCB at Layer 2 while spanning tree stays inside each site.
The core router already runs PIM sparse mode with 3.3.3.3 as the RP. Use it as the OTV control plane: the edges find each other through a shared control group instead of an adjacency server.
OTV is configured on both data centers and the overlay adjacency is up, yet PCA cannot reach PCB. Find out why the edges refuse to extend VLAN 10 to each other and fix it.
Two spines and two leaves are cabled as a full mesh. With classic spanning tree half of those links would be blocked. Build a FabricPath fabric instead: every link forwards, and each leaf reaches the other over both spines.
SW3 is a classic Ethernet switch with one uplink to each leaf. The FabricPath edge switches act as one spanning-tree bridge (c84c.75fa.6000) toward it, but SW3 currently has the better bridge ID, so the leaves block their edge ports and PC3 is cut off. Make the fabric the root.
SW3 bundles its two uplinks into Port-channel20 with LACP, one to each leaf. Inside a FabricPath fabric the leaves pair up with vPC+: a vPC domain whose peer-link is a FabricPath port and which is known to the rest of the fabric as one emulated switch-id.
The fabric is cabled and FabricPath is enabled everywhere, yet PC1 cannot reach PC2. There are two faults. Find them with the FabricPath show commands and fix them.
L1 and L2 are leaves joined only by a routed underlay (OSPF through S1). Both have hosts in VLAN 10. Stretch VLAN 10 across the underlay with VXLAN: map it to VNI 10010 and replicate broadcast and unknown traffic to the other VTEP by unicast.
The underlay already runs PIM sparse mode on every link and loopback, with S1 (3.3.3.3) as the RP. Let the underlay replicate VNI 10010’s broadcast and unknown traffic: both leaves join one multicast group for the VNI.
Replace flood-and-learn with a control plane. S1 becomes an iBGP route reflector for the L2VPN EVPN address family; each leaf advertises its VNI (a type-3 route) and its hosts (type-2 routes), and the leaves find each other from those routes.
BGP EVPN is configured on the fabric and every BGP session is up, but the leaves do not list each other as NVE peers and PC1 cannot reach PC2. There are two faults, one on each leaf.
The BGP EVPN fabric carries VLAN 10 (VNI 10010) on L1 and VLAN 20 (VNI 10020) on L2, but nothing routes between them. Add a tenant VRF with a Layer 3 VNI: each leaf is the anycast gateway of its subnet, and traffic between subnets is routed into VNI 50000, carried to the other leaf and routed again there (symmetric IRB).
L2 is also the border leaf: in VRF TENANT it reaches an outside network, stood in for by loopback100 (10.100.100.0/24). Hosts have type-2 routes, but a whole prefix needs a type-5 (IP prefix) route. Advertise it into EVPN.
The tenant VRF is configured on both leaves and each host reaches its own gateway, yet PC1 cannot reach PC2 in the other subnet. One piece of the Layer 3 VNI is missing on each leaf.