class ExtIntTable

Make two route RouteTables behave like one, while resolving nexthops that are not immediate neighbors. More...

Definition#include <rt_tab_extint.hh>
Template formExtIntTable<class A>
InheritsRouteTable [public ]
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Detailed Description

ExtIntTable takes two routing tables and combines them together to form a single table, where routes for the same subnet with a lower admin distance override those with a higher admin distance. The two parent tables are different: the Internal table takes routes only from IGP protocols, and so the nexthops of routes it provides are always immediate neighbors. The External table takes routes from EGP protocols, and so the nexthops of routes it provides may not be immediate neighbors. The ExtIntTable resolves the nexthops of all routes it propagates downstream. If a nexthop cannot be resolved, it is not propagated downstream, but is stored pending the arrival of a route that would permit the nexthop to be resolved.

An add_route request from a parent tables causes a lookup on the other parent table. If the route is better than the one from the other table, or no route exists in the other table, then the new route is passed downstream.

An delete_route request from a parent table also causes a lookup on the other parent table. The delete_route is propagated downstream. If an alternative route is found, then that is then propagated downsteam as an add_route to replace the deleted route.

Lookups from downsteam cause lookups on both parent tables. The better response is given.

A RIB normally only has one ExtIntTable.

 ExtIntTable (const string& tblname, RouteTable<A> *ext_table, RouteTable<A> *int_table)

ExtIntTable

ExtIntTable Constructor.

Parameters:
tablenamehuman-readable tablename to aid debugging
ext_tableparent RouteTables supplying EGP routes
int_tableparent RouteTables supplying IGP routes

int  add_route (const IPRouteEntry<A>& route, RouteTable<A> *caller)

add_route

An add_route request from a parent table causes a lookup on the other parent table. If the route is better than the one from the other table, or no route exists in the other table then it is passed downstream if nexthop resolution is successful.

Parameters:
routethe new route
callerthe parent table sending the new route

Reimplemented from RouteTable.

int  delete_route (const IPRouteEntry<A> *route, RouteTable<A> *caller)

delete_route

An delete_route request from a parent table also causes a lookup on the other parent table. The delete_route is propagated downstream. If an alternative route is found and nexthop resolution on it is successful, then it is then propagated downsteam as an add_route to replace the deleted route

Parameters:
routethe route to be deleted.
callerthe parent table sending the delete_route.

Reimplemented from RouteTable.

const IPRouteEntry<A> * lookup_route (const IPNet<A>& net)

lookup_route

[const]

Lookup a specific subnet. The lookup will first look in the ExtIntTable 's table of resolved routes - if there is a route here, then this is returned. Otherwise the lookup will be sent to both parent tables. If both give an answer, then the route with the better admin_distance is returned, so long as it gives a nexthop that is resolvable.

Parameters:
netthe subnet to look up.

Returns: a pointer to the route entry if it exists, NULL otherwise.

Reimplemented from RouteTable.

const IPRouteEntry<A> * lookup_route (const A& addr)

lookup_route

[const]

Lookup an IP address to get the most specific (longest prefix length) route that matches this address. The lookup will be sent to both parent tables and the ExtIntTable's internal table of resolved_routes. The most specific answer is returned, so long as the nexthop resolves. If more than one route has the same prefix length, then the route with the better admin_distance is returned.

Parameters:
addrthe IP address to look up.

Returns: a pointer to the best most specific route entry if any entry matches and its nexthop resolves, NULL otherwise.

Reimplemented from RouteTable.

RouteRange<A> * lookup_route_range (const A& addr)

lookup_route_range

[const]

Lookup an IP address to get the most specific (longest prefix length) route that matches this address, along with the RouteRange information for this address and route. As with lookup_route, this involves querying ExtIntTable's resolved_routes table and possibly both parent tables. The best, most specific route is returned if the nexthop is resolvable, and the tightest bounds on the answer are returned.

Parameters:
addrthe IP address to look up.

Returns: a pointer to a RouteRange class instance containing the relevant answer. It is up to the recipient of this pointer to free the associated memory.

See also: RouteRange

Reimplemented from RouteTable.

int  type ()

type

[const]

Returns: EXTINT_TABLE

Reimplemented from RouteTable.

void  replumb (RouteTable<A> *old_parent, RouteTable<A> *new_parent)

replumb

replumb the parent tables, so that new_parent replaces old_parent

Parameters:
new_parent

Reimplemented from RouteTable.

string  str ()

str

[const]

Render this ExtIntTable as a string for debugging purposes

Reimplemented from RouteTable.


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