Just-in time forwarding information base

A router comprising:

• a line card including a memory that stores a local routing table, configured to:
• request a routing entry from a routing table,
• receive the routing entry,
• insert the routing entry in the local routing table, and
• age out stale routing entries from the local routing table;
• and
• a control module including the routing table, configured to:
• distribute the routing entry in the routing table to the line card in response to the request from the line card;
• wherein the line card is further configured to:
• receive a first packet, and
• identify the first packet as a domain name system (DNS) request;
• wherein the control module is further configured to:
• send a request to other routers to send copies of replies to the DNS request to the router;
• wherein the line card is further configured to:
• receive a DNS reply in response to the request to the other routers,
• determine whether the local routing table includes a DNS flow entry corresponding to an address resolved by the DNS reply, and
• notify the control module when the local routing table does not include the DNS flow entry;
• wherein the control module is further configured to:
• lookup the DNS flow entry in the routing table, and
• populate the local routing table with the DNS flow entry,
• wherein the DNS flow entry comprises an Internet Protocol address of an authoritative DNS,
• wherein, when populating the local routing table with the DNS flow entry, the control module is further configured to set a flag in the DNS flow entry to indicate whether the routing table includes a second routing entry whose corresponding address prefix matches that of the DNS flow entry, wherein the corresponding address prefix of the second routing entry is longer than that of the DNS flow entry,
• wherein the local routing table includes one of a local forwarding information base (local FIB) or a local label forwarding information base (local LFIB), and
• wherein the routing table includes a best routing information base (BRIB).

A method comprising:

• requesting, by a line card of a router, a routing entry from a routing table, wherein the line card stores a local routing table;
• receiving, by the line card, the routing entry;
• inserting, by the line card, the routing entry in the local routing table;
• aging out, by the line card, stale routing entries from the local routing table;
• distributing, by a control module of the router, the routing entry in the routing table to the line card in response to the request from the line card, wherein the control module includes the routing table;
• receiving, by the line card, a first packet;
• identifying, by the line card, the first packet as a domain name system (DNS) request;
• sending, by the control module, a request to other routers to send copies of replies to the DNS request to the router;
• receiving, by the line card, a DNS reply in response to the request to the other routers;
• determining, by the line card, whether the local routing table includes a DNS flow entry corresponding to an address resolved by the DNS reply;
• notifying, by the line card, the control module when the local routing table does not include the DNS flow entry;
• looking up, by the control module, the DNS flow entry in the routing table;
• and
• populating, by the control module, the local routing table with the DNS flow entry,
• wherein the DNS flow entry comprises an Internet Protocol address of an authoritative DNS,
• wherein populating the local routing table with the DNS flow entry further includes setting, by the control module, a flag in the DNS flow entry to indicate whether the routing table includes a second routing entry whose corresponding address prefix matches that of the DNS flow entry,
• wherein the corresponding address prefix of the second routing entry is longer than that of the DNS flow entry,
• wherein the local routing table includes one of a local forwarding information base (local FIB) or a local label forwarding information base (local LFIB), and
• wherein the routing table includes a best routing information base (BRIB).