A host has an address on 192.168.1.0/24 but no default route. The router is 192.168.1.1. Which command installs the default gateway for the running system?
LPIC-1 Exam 102-500, objective 109. Networking fundamentals medium
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The options
Correct ip route add default via 192.168.1.1
Correct. `default` is shorthand for the destination 0.0.0.0/0, and `via` names the next-hop router. The legacy equivalent is `route add default gw 192.168.1.1`.
Not correct ip route add 192.168.1.1 default
Wrong. The syntax is inverted: `ip route add` expects the destination prefix first, then `via NEXTHOP`. As written it would be parsed as a route to the host 192.168.1.1 and rejected.
Not correct ip addr add default via 192.168.1.1
Wrong object. `ip addr` manages interface addresses; routes are not addresses and this command is a syntax error.
Not correct ip neigh add default 192.168.1.1
Wrong. `ip neigh` manipulates the neighbour (ARP) cache, mapping IP addresses to link-layer addresses on the local segment. It cannot create routes.
Why
The default route matches any destination not covered by a more specific route and sends it to the next-hop router. Add it with `ip route add default via GATEWAY [dev IFACE]`, inspect it with `ip route show`, and remove it with `ip route del default`. Like `ip addr add`, this change lives only in the running kernel; persistence comes from /etc/network/interfaces, NetworkManager, or DHCP.
Where this comes from
- Cited
- manual page ip-route(8)
Practise this
Reading one question is not practice. The trainer will draw a set from objective 109 and space the ones you get wrong.