Score Higher on Verified JN0-280 | Data Center, Associate (JNCIA-DC) Exam Questions with Answers

In Junos OS, routing information is stored in different routing tables depending on the protocol and address family. For IPv6 addresses, the routing table used isinet6.0.

Step-by-Step Explanation:

Routing Tables in Junos:

inet.0: This is the primary routing table for IPv4 unicast routes.

inet6.0: This is the primary routing table for IPv6 unicast routes.

inet.3: This routing table is used for MPLS-related routing.

Other routing tables, like inet.1, inet.2, are used for multicast and other specific purposes.

inet6.0 Routing Table:When IPv6 is enabled on a Juniper router, all the IPv6 routes are stored in theinet6.0table. This includes both direct routes (connected networks) and learned routes (from dynamic routing protocols like OSPFv3, BGP, etc.).

Verification:To view IPv6 routes, the command show route table inet6.0 is used. This will display the contents of the IPv6 routing table, showing the network prefixes, next-hop addresses, and protocol information for each route.

Juniper Reference:

Junos Command: Use show route table inet6.0 to check IPv6 routing entries.

IPv6 Routing: Ensure that the IPv6 protocol is enabled on interfaces and that routingprotocols like OSPFv3 or BGP are properly configured for IPv6 traffic handling.

Aggregate routesandgenerated routesare used to create summarized routes in Junos, but they behave differently in terms of forwarding.

Step-by-Step Breakdown:

Aggregate Routes:

Anaggregate routesummarizes a set of more specific routes, but it does not have a direct forwarding next hop. Instead, it points to the more specific routes for actual packet forwarding.

Generated Routes:

Agenerated routealso summarizes specific routes, but it has aforwarding next hopthat is determined based on the availability of contributing routes. The generated route can be used to directly forward traffic.

Juniper Reference:

Aggregate and Generated Routes: In Junos, aggregate routes rely on more specific routes for forwarding, while generated routes can forward traffic directly based on their next-hop information.

When thediscardoption is configured as the next hop for a static route, it silently drops any packets that match the route without sending any notification to the sender.

Step-by-Step Breakdown:

Discard Behavior:

If a route uses thediscardnext hop, the router drops the packet without generating any ICMP message or error back to the sender. This is useful for creating null routes to prevent routing loops or blackhole traffic intentionally.

Reject vs. Discard:

Therejectnext hop, in contrast, drops the packet but sends anICMP Destination Unreachablemessage back to the source.

Juniper Reference:

Static Route Behavior: In Junos, thediscardoption ensures packets matching a static route are dropped silently, providing a way to discard traffic without alerting the source.