300-410 Layer 3 Technologies Practice Test 8 — 15 Questions

Question 1

A network engineer is configuring policy-based routing (PBR) on a Cisco IOS XE router. A route-map named PBR-MAP is applied to interface GigabitEthernet0/0 with the command `ip policy route-map PBR-MAP`. The route-map contains a single sequence: `route-map PBR-MAP permit 10` with `match ip address 101` and `set ip next-hop 10.1.1.2`. Access-list 101 permits traffic from 192.168.1.0/24 to any destination. After applying the configuration, the engineer notices that traffic from 192.168.1.0/24 is still being forwarded according to the routing table instead of the next-hop 10.1.1.2. Which action will resolve this issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Enable `ip policy route-map PBR-MAP` on the ingress interface of the traffic.. Policy-based routing must be applied on the interface where the traffic enters the router (ingress). If the route-map is applied on an egress interface, the router will forward the packet based on the routing table before the policy is evaluated. Moving the `ip policy route-map` command to the ingress interface ensures that the route-map is processed first, allowing the `set ip next-hop` to take effect.

Answer

Modify access-list 101 to permit all traffic instead of only 192.168.1.0/24.

Answer

Configure `ip local policy route-map PBR-MAP` to apply the policy to all interfaces.

Answer

Add the `set ip default next-hop 10.1.1.2` command to the route-map.

Question 2

A network engineer is configuring a Cisco IOS XE router to connect to an MPLS Layer 3 VPN service provider. The engineer needs to exchange routes with the provider's PE router using BGP. The provider has assigned the customer an AS number of 65001, and the PE router uses AS 65000. The engineer wants to ensure that the BGP session is established and routes are exchanged correctly. Which BGP configuration is required on the CE router?

Accepted Answer

Configure the CE router with `neighbor <PE-IP> remote-as 65000` and advertise the customer's networks using the `network` command.. In an MPLS L3VPN, the CE router peers with the PE router using eBGP. The CE must configure the PE as an eBGP neighbor with the correct remote AS number (the PE's AS) and advertise its local networks into BGP. This allows the PE to learn the customer routes and distribute them through the MPLS VPN. Other options are either incorrect AS configuration or unnecessary features.

Answer

Configure the CE router with `neighbor <PE-IP> remote-as 65001` to form an iBGP session with the PE router.

Answer

Configure the CE router with `neighbor remote-as 65000` and enable `neighbor send-community`.

Answer

Configure the CE router with `neighbor remote-as 65000` and enable `neighbor next-hop-self`.

Question 3

A network engineer is configuring policy-based routing (PBR) on a Cisco IOS XE router. The engineer wants to route traffic from a specific source subnet to a next-hop IP that is not in the routing table, using a route-map. The route-map must match packets based on source address and set the next-hop to 192.168.2.1. Which two statements are true about this configuration? (Choose two.)

Accepted Answer

The `set ip next-hop` command can be used to set a next-hop that is not in the routing table, and the router will use it without any reachability check by default.. The `set ip next-hop` command in PBR can specify a next-hop that is not in the routing table, and by default it does not verify reachability. To ensure the next-hop is reachable before applying the policy, the `verify-availability` keyword can be used, which checks reachability via ARP or a tracking object. These two behaviors are key to understanding PBR next-hop handling.

Answer

The `set ip next-hop` command requires that the next-hop IP be reachable via a route in the routing table, otherwise the route-map will not be applied.

Answer

The `set ip next-hop` command requires the next-hop to be a directly connected interface, and the route-map will not be applied if the next-hop is not directly connected.

Answer

The `set ip next-hop` command requires that the next-hop IP be directly connected to the router, otherwise the route-map will not be applied.

Question 4

A network engineer is configuring a Cisco IOS XE router to redistribute routes from OSPF into EIGRP. The engineer wants to ensure that only specific OSPF routes are redistributed and that the redistribution is not causing routing loops. The engineer uses a route-map named OSPF-TO-EIGRP with a match on a prefix-list. However, after applying the configuration, the engineer notices that some OSPF routes are still being redistributed even though they are not permitted by the prefix-list. Which action should the engineer take to resolve this issue?

Accepted Answer

Add a `deny` statement at the end of the prefix-list to block all other routes.. When using a route-map for redistribution, the route-map must have a match condition that references the prefix-list. If the route-map has a permit statement without a match, or if the prefix-list is not properly denying unwanted routes, all routes may be permitted. Prefix-lists have an implicit deny at the end, but an explicit deny ensures clarity. The most direct solution is to ensure the prefix-list explicitly denies unwanted routes and permits only the desired ones, and that the route-map matches that prefix-list.

Answer

Apply the prefix-list directly to the OSPF process using the `distribute-list` command.

Answer

Configure the route-map with a `deny` sequence to block unwanted routes.

Answer

Add a `set` statement to the route-map to tag redistributed routes.

Question 5

A network engineer is implementing BGP route reflectors in an IBGP network. The engineer configures R1 as a route reflector with two clients, R2 and R3. R1 is also a client of another route reflector, R4. R2 advertises a route to R1. Which routers will receive this route from R1?

Accepted Answer

Both R3 and R4. According to BGP route reflection rules, when a route reflector receives a route from a client, it reflects that route to all other clients and to all non-client IBGP peers. In this scenario, R1 receives the route from R2 (a client), so it reflects it to R3 (another client) and to R4 (a non-client). Therefore, both R3 and R4 will receive the route.

Answer

R3 only

Answer

R4 only

Answer

Neither R3 nor R4

Question 6

A network engineer is configuring EIGRP for IPv6 on a Cisco IOS-XE router. The engineer wants to enable EIGRP on interface GigabitEthernet0/0 and ensure that the router participates in EIGRP autonomous system 100. Which configuration is correct?

Accepted Answer

ipv6 router eigrp 100, then interface GigabitEthernet0/0, then ipv6 eigrp 100. The correct configuration enables the EIGRP for IPv6 process globally with ipv6 router eigrp 100, then activates it on the interface with ipv6 eigrp 100. The other options use incorrect commands or omit necessary steps. The router ID must also be set, but that is not part of the options.

Answer

router eigrp 100, then interface GigabitEthernet0/0, then ipv6 eigrp 100

Answer

ipv6 router eigrp 100, then interface GigabitEthernet0/0, then ipv6 router eigrp 100

Answer

ipv6 unicast-routing, then ipv6 router eigrp 100, then interface GigabitEthernet0/0, then ipv6 eigrp 100

Question 7

A network engineer is configuring EIGRP on a Cisco IOS XE router. The engineer wants to limit the scope of EIGRP queries to prevent them from propagating beyond a specific router. Which EIGRP feature should the engineer configure on the interface facing the remote network?

Accepted Answer

EIGRP stub routing or route summarization to create a query boundary. To limit EIGRP query propagation, you can configure a router as a stub or use route summarization. Stub routing prevents the router from being queried for routes it does not have, while summarization creates a boundary where queries for more specific routes are not forwarded. Both methods effectively scope queries and prevent them from propagating beyond a certain point.

Answer

EIGRP route summarization

Answer

EIGRP query scoping with the `eigrp query-scope` command

Answer

EIGRP stub routing

Question 8

A network engineer is configuring a Cisco IOS XE router for OSPFv2. The router is an ABR connected to Area 0 and Area 1. Area 1 is a not-so-stubby area (NSSA). The engineer wants to summarize the Type-7 LSAs from Area 1 into Type-5 LSAs for Area 0. Which command should the engineer use on the ABR to accomplish this?

Accepted Answer

summary-address 10.1.0.0 255.255.0.0. In an NSSA, the ABR translates Type-7 LSAs from the NSSA into Type-5 LSAs for the backbone area. To summarize these external routes, the ABR uses the `summary-address` command. This command aggregates the external routes into a single Type-5 LSA, reducing the number of LSAs and improving scalability. The `area range` command is used for inter-area summarization, and `translate type7 suppress-fa` only affects the forwarding address, not summarization.

Answer

area 1 nssa translate type7 suppress-fa

Answer

redistribute ospf 1 match internal external

Answer

area 1 range 10.1.0.0 255.255.0.0

Question 9

A network engineer is configuring policy-based routing (PBR) on a Cisco IOS-XE router. The engineer wants to route traffic from subnet 10.10.10.0/24 that is destined for any address to next-hop 192.168.1.1, except for traffic destined to 10.20.20.0/24, which should be routed normally. Which configuration achieves this?

Accepted Answer

route-map PBR permit 10; match ip address 101; set ip next-hop 192.168.1.1; route-map PBR permit 20; access-list 101 deny ip 10.10.10.0 0.0.0.255 10.20.20.0 0.0.0.255; access-list 101 permit ip 10.10.10.0 0.0.0.255 any. Policy-based routing uses route maps to match traffic and set attributes like next-hop. To exclude specific traffic from being policy-routed, the access list used in the match statement must deny that traffic before permitting the rest. The denied traffic will not match the route-map sequence and will be evaluated against subsequent sequences. A final permit sequence without a match ensures that all other traffic is routed normally without PBR. This design correctly routes traffic to 10.20.20.0/24 via the normal routing table while policy-routing other traffic from 10.10.10.0/24.

Answer

route-map PBR permit 10; match ip address 101; set ip next-hop 192.168.1.1; route-map PBR permit 20; access-list 101 permit ip 10.10.10.0 0.0.0.255 any; access-list 101 deny ip 10.10.10.0 0.0.0.255 10.20.20.0 0.0.0.255

Answer

route-map PBR permit 10; match ip address 101; set ip next-hop 192.168.1.1; access-list 101 deny ip 10.10.10.0 0.0.0.255 10.20.20.0 0.0.0.255; access-list 101 permit ip 10.10.10.0 0.0.0.255 any

Answer

route-map PBR permit 10; match ip address 101; set ip next-hop 192.168.1.1; route-map PBR permit 20; access-list 101 permit ip 10.10.10.0 0.0.0.255 any

Question 10

A network engineer is configuring BGP on a Cisco IOS XE router. The router is peering with an ISP and receives a full BGP table. The engineer wants to filter incoming routes so that only routes with a specific community value (65000:100) are accepted, and all other routes are discarded. Which BGP configuration achieves this?

Accepted Answer

Configure a route-map with a community match for 65000:100 and a permit statement, and another sequence that denies all, then apply it inbound on the neighbor.. To accept only routes with a specific community and discard others, you need a route-map that permits matching routes and denies all others, applied inbound. The route-map should have a permit sequence matching the community and a deny sequence for everything else. This ensures only routes with the desired community are accepted.

Answer

Configure an inbound filter using a standard community list that permits 65000:100 and denies everything else, then apply it with `neighbor x.x.x.x filter-list`.

Answer

Configure a route-map with `match community 65000:100` and apply it as an inbound filter on the neighbor. Use `ip community-list standard` to define the community.

Answer

Configure a route-map that denies all routes, then use `set community` to add the community, and apply it outbound.

Question 11

A network engineer is configuring BGP on a Cisco IOS XE router. The router has two eBGP peers: one in AS 65001 and one in AS 65002. The engineer wants to influence outbound traffic by preferring the path through AS 65001. Which BGP attribute should be modified, and how, to accomplish this?

Accepted Answer

Set a higher weight for routes learned from AS 65001.. Weight is a Cisco-specific BGP attribute that is local to the router and is evaluated first in the BGP best path selection algorithm. It is not advertised to any BGP peer, so it can be used to prefer one eBGP peer over another for outbound traffic. Setting a higher weight for routes from AS 65001 ensures that the router selects those routes over routes from AS 65002. Other attributes like local preference and MED serve different purposes and are not suitable for this scenario.

Answer

Set a higher local preference for routes learned from AS 65001.

Answer

Prepend the AS path with AS 65001's AS number when advertising routes to AS 65002.

Answer

Set a lower multi-exit discriminator (MED) for routes advertised to AS 65001.

Question 12

A network engineer is configuring a Cisco IOS XE router as a DHCP relay. The router has two interfaces: GigabitEthernet0/0 (10.1.1.1/24) facing clients and GigabitEthernet0/1 (192.168.1.1/30) facing the DHCP server at 192.168.1.2. The engineer enters the command `ip helper-address 192.168.1.2` under interface GigabitEthernet0/0. However, clients are not receiving IP addresses. What is the most likely cause?

Accepted Answer

An access control list or firewall is blocking UDP ports 67 and 68 between the router and the DHCP server.. The relay agent forwards DHCP broadcasts as unicast to the server using UDP ports 67 and 68. Even with correct `ip helper-address` placement, an ACL or firewall blocking these ports will prevent address assignment. The other options misidentify the required interface, incorrectly require a static route, or confuse the DHCP server service with the relay agent.

Answer

The `ip helper-address` command must be configured on the interface closest to the DHCP server, not the client-facing interface.

Answer

The DHCP server is on a different subnet, so the router cannot relay DHCP requests without a static route to the server.

Answer

The `ip helper-address` command requires the `service dhcp` global configuration command to be enabled.

Question 13

A network engineer is configuring Policy-Based Routing (PBR) on a Cisco IOS XE router. The engineer wants traffic from the 10.1.1.0/24 subnet to be forwarded to next-hop 192.168.1.2, but only if the destination is 172.16.1.0/24. All other traffic from that subnet should use the normal routing table. The engineer creates a route map named PBR-MAP with a sequence 10 that matches an ACL for 10.1.1.0/24 and sets the next-hop to 192.168.1.2, and applies it to interface GigabitEthernet0/0 with the command `ip policy route-map PBR-MAP`. However, traffic to 172.16.1.0/24 is not being policy-routed. What is the most likely cause?

Accepted Answer

The ACL used in the route map must match the destination subnet 172.16.1.0/24, not the source subnet 10.1.1.0/24.. Policy-Based Routing on Cisco IOS XE uses route maps to match traffic and set forwarding actions. The match criteria in the route map's ACL should identify the traffic that needs special handling. In this scenario, the engineer wants to policy-route traffic destined to 172.16.1.0/24, so the ACL must match that destination subnet. Matching the source subnet 10.1.1.0/24 would incorrectly apply PBR to all traffic from that source, which is not the desired outcome.

Answer

The next-hop IP address 192.168.1.2 is not reachable via the routing table, so PBR cannot use it.

Answer

The route map sequence 10 is missing a `set` clause to define the action for matched traffic.

Answer

The route map must be applied with the `ip policy route-map PBR-MAP` command on the ingress interface, but it was applied on the egress interface.

Question 14

A network engineer is configuring a Cisco IOS XE router for MPLS Layer 3 VPN. The router is a PE router that must exchange VPNv4 routes with another PE router. The engineer has enabled MPLS LDP on the core interfaces and configured VRFs. Which two additional configurations are required to establish the MP-BGP session and exchange VPNv4 routes? (Choose two.)

Accepted Answer

Configure a route distinguisher (RD) and route target (RT) for each VRF.. To exchange VPNv4 routes between PE routers, MP-BGP must be configured with the VPNv4 address family and the neighbor must be activated under that address family. Additionally, each VRF requires a unique route distinguisher and route targets to ensure proper route import and export. These configurations are essential for MPLS L3VPN operation. Enabling MPLS on core interfaces and configuring VRFs on customer interfaces are already done or not directly related to the MP-BGP session setup.

Answer

Enable OSPF as the IGP and configure it to advertise the loopback addresses of the PE routers.

Answer

Enable 'mpls ip' on the PE router's core-facing interfaces.

Answer

Configure 'ip vrf forwarding' on the PE router's core-facing interfaces.

Question 15

A network engineer is implementing MPLS Layer 3 VPN on a Cisco IOS XE router. The engineer configures a VRF named CUSTOMER on the PE router and assigns interface GigabitEthernet0/1 to it. The PE router must exchange VPNv4 routes with a remote PE router using MP-BGP. The engineer configures BGP with the address-family vpnv4 and activates the neighbor. However, the remote PE router does not receive the VPNv4 routes. Which additional configuration is required on the PE router to allow the VPNv4 routes to be advertised?

Accepted Answer

Configure a route distinguisher (RD) under the VRF definition.. For MPLS Layer 3 VPN, each VRF on a PE router must have a unique route distinguisher (RD) to create unique VPNv4 prefixes. The RD is prepended to the IPv4 prefix, forming a VPNv4 address that is advertised via MP-BGP. Without an RD, the PE router cannot generate VPNv4 routes for the VRF, so no VPNv4 updates are sent. Route targets are important for import/export but are not the immediate cause of the failure to advertise.

Answer

Configure a route target (RT) export under the VRF definition.

Answer

Configure the `neighbor x.x.x.x activate` command under the IPv4 address family.

Answer

Enable the `send-community extended` command under the BGP neighbor configuration.