Loopback interfaces are virtual logical interfaces on NX-OS that provide a stable, always-up reference point for network services including routing protocol router IDs, management access, and service endpoints that remain accessible regardless of physical interface states. They support full Layer 3 functionality including IPv4 and IPv6 addressing with secondary addresses, VRF membership, link logging, and routing protocol participation through OSPF, OSPFv3, PIM, and IS-IS sub-sections. Loopback interfaces also support DHCP relay, IPv6 neighbor discovery configuration, ICMPv6 controls (redirects, unreachables), access group filtering, and are essential for VXLAN VTEP source interfaces, BGP peering, and overlay network anchor points.
Loopback interfaces are virtual logical interfaces on NX-OS that provide a stable, always-up reference point for network services including routing protocol router IDs, management access, and service endpoints that remain accessible regardless of physical interface states. They support full Layer 3 functionality including IPv4 and IPv6 addressing with secondary addresses, VRF membership, link logging, and routing protocol participation through OSPF, OSPFv3, PIM, and IS-IS sub-sections. Loopback interfaces also support DHCP relay, IPv6 neighbor discovery configuration, access group filtering, and are essential for VXLAN VTEP source interfaces, BGP peering, and overlay network anchor points.
Name Type Constraint Mandatory Default Value configuration Class configuration No
Name Type Constraint Mandatory Default Value configuration Class configuration No
Name Type Constraint Mandatory Default Value configuration Class configuration No
Name Type Constraint Mandatory Default Value configuration Class configuration No
Name Type Constraint Mandatory Default Value interfaces Class interfaces No
Name Type Constraint Mandatory Default Value loopbacks List loopbacks No
Name Type Constraint Mandatory Default Value id Integer min: 0 Yes interface_ groups List String No shutdown Boolean true, falseNo description String No logging_ event_ port_ link_ status Boolean true, falseNo vrf String No ip Class ip No ipv6 Class ipv6 No ospf Class ospf No ospfv3 Class ospfv3 No pim Class pim No isis Class isis No bfd Class bfd No nd Class nd No
Name Type Constraint Mandatory Default Value id Integer min: 0 Yes interface_ groups List String No shutdown Boolean true, falseNo description String No logging_ event_ port_ link_ status Boolean true, falseNo vrf String No ip Class ip No ipv6 Class ipv6 No ospf Class ospf No ospfv3 Class ospfv3 No pim Class pim No isis Class isis No nd Class nd No
Name Type Constraint Mandatory Default Value address IP No tag Integer min: 0, max: 4294967295 No secondary_ addresses List secondary_ addresses No forward Boolean true, falseNo drop_glean Boolean true, falseNo unnumbered String No directed_ broadcast Boolean true, falseNo directed_ broadcast_ acl String No redirects Boolean true, falseNo unreachables Boolean true, falseNo port_ unreachable Boolean true, falseNo verify_ unicast_ source_ reachable_ via Choice disabled, rx, any, any-allow-default, rx-allow-vni-hostsNo access_group_in String No access_ group_ out String No dhcp_ relay_ information_ trusted Boolean true, falseNo dhcp_ relay_ smart_ relay Boolean true, falseNo dhcp_ relay_ subnet_ broadcast Boolean true, falseNo dhcp_ relay_ information_ option Boolean true, falseNo dhcp_ relay_ source_ subnet String No dhcp_ relay_ addresses List dhcp_ relay_ addresses No
Name Type Constraint Mandatory Default Value address IP No tag Integer min: 0, max: 4294967295 No secondary_ addresses List secondary_ addresses No forward Boolean true, falseNo drop_glean Boolean true, falseNo unnumbered String No directed_ broadcast Boolean true, falseNo directed_ broadcast_ acl String No redirects Boolean true, falseNo unreachables Boolean true, falseNo port_ unreachable Boolean true, falseNo verify_ unicast_ source_ reachable_ via Choice disabled, strict, loose, loose-allow-default, strict-allow-vni-hostsNo access_group_in String No access_ group_ out String No dhcp_ relay_ information_ trusted Boolean true, falseNo dhcp_ relay_ smart_ relay Boolean true, falseNo dhcp_ relay_ subnet_ broadcast Boolean true, falseNo dhcp_ relay_ information_ option Boolean true, falseNo dhcp_ relay_ source_ subnet String No dhcp_ relay_ addresses List dhcp_ relay_ addresses No
Name Type Constraint Mandatory Default Value address IP No secondary_ addresses List IP No forward Boolean true, falseNo drop_glean Boolean true, falseNo unnumbered String No directed_ broadcast Boolean true, falseNo directed_ broadcast_ acl String No redirects Boolean true, falseNo unreachables Boolean true, falseNo port_ unreachable Boolean true, falseNo verify_ unicast_ source_ reachable_ via Choice disabled, strict, loose, loose-allow-default, strict-allow-vni-hostsNo access_group_in String No access_ group_ out String No dhcp_ relay_ information_ trusted Boolean true, falseNo dhcp_ relay_ smart_ relay Boolean true, falseNo dhcp_ relay_ subnet_ broadcast Boolean true, falseNo dhcp_ relay_ information_ option Boolean true, falseNo dhcp_ relay_ source_ subnet String No dhcp_ relay_ addresses List dhcp_ relay_ addresses No
Name Type Constraint Mandatory Default Value address_ autoconfig Boolean true, falseNo nd_ default_ route Boolean true, falseNo forward Boolean true, falseNo link_ local_ use_ bia Boolean true, falseNo address_ use_ link_ local_ only Boolean true, falseNo verify_ unicast_ source_ reachable_ via Choice disabled, rx, any, any-allow-default, rx-allow-vni-hostsNo address_ link_ local IP No addresses List addresses No dhcp_ smart_ relay Boolean true, falseNo dhcp_ relay_ addresses List dhcp_ relay_ addresses No redirects Boolean true, falseNo unreachables Boolean true, falseNo
Name Type Constraint Mandatory Default Value address_ autoconfig Boolean true, falseNo nd_ default_ route Boolean true, falseNo forward Boolean true, falseNo link_ local_ use_ bia Boolean true, falseNo address_ use_ link_ local_ only Boolean true, falseNo verify_ unicast_ source_ reachable_ via Choice disabled, strict, loose, loose-allow-default, strict-allow-vni-hostsNo address_ link_ local String No addresses List addresses No dhcp_ smart_ relay Boolean true, falseNo dhcp_ relay_ addresses List dhcp_ relay_ addresses No redirects Boolean true, falseNo unreachables Boolean true, falseNo
Name Type Constraint Mandatory Default Value address_ autoconfig Boolean true, falseNo nd_ default_ route Boolean true, falseNo forward Boolean true, falseNo link_ local_ use_ bia Boolean true, falseNo address_ use_ link_ local_ only Boolean true, falseNo verify_ unicast_ source_ reachable_ via Choice disabled, strict, loose, loose-allow-default, strict-allow-vni-hostsNo address_ link_ local String No addresses List addresses No dhcp_ smart_ relay Boolean true, falseNo dhcp_ relay_ addresses List dhcp_ relay_ addresses No
Name Type Constraint Mandatory Default Value process String Yes advertise_ secondaries Boolean true, falseNo advertise_ subnet Boolean true, falseNo area Any IP or Integer[min: 0, max: 4294967295] No bfd Boolean true, falseNo cost Integer min: 0, max: 65535 No dead_interval Integer min: 0, max: 65535 No hello_interval Integer min: 0, max: 65535 No mtu_ignore Boolean true, falseNo network Choice point-to-point, broadcastNo prefix_ attributes_ n_ flag_ clear Choice unspecified, clearNo passive_ interface Boolean true, falseNo priority Integer min: 0, max: 255 No retransmit_ interval Integer min: 1, max: 65535 No transmit_delay Integer min: 1, max: 450 No authentication_ key String No message_ digest_ key_ id Integer min: 0, max: 255 No authentication_ key_ secure_ mode Boolean true, falseNo authentication_ key_ chain String No message_ digest_ key String No message_ digest_ key_ secure_ mode Boolean true, falseNo authentication Choice simple, md5, noneNo
Name Type Constraint Mandatory Default Value process String Yes advertise_ secondaries Boolean true, falseNo advertise_ subnet Boolean true, falseNo area String No bfd Boolean true, falseNo cost Integer min: 0, max: 65535 No dead_interval Integer min: 0, max: 65535 No hello_interval Integer min: 0, max: 65535 No mtu_ignore Boolean true, falseNo network Choice unspecified, p2p, bcastNo prefix_ attribute_ n_ flag Choice unspecified, clearNo passive_ interface Boolean true, falseNo priority Integer min: 0, max: 255 No retransmit_ interval Integer min: 1, max: 65535 No transmit_delay Integer min: 1, max: 450 No authentication_ key String No message_ digest_ key_ id Integer min: 0, max: 255 No authentication_ key_ secure_ mode Boolean true, falseNo authentication_ key_ chain String No message_ digest_ key String No message_ digest_ key_ secure_ mode Boolean true, falseNo authentication Choice unspecified, simple, md5, noneNo
Name Type Constraint Mandatory Default Value process String Yes advertise_ secondaries Boolean true, falseNo area Any IP or Integer[min: 0, max: 4294967295] No bfd Boolean true, falseNo cost Integer min: 0, max: 65535 No dead_interval Integer min: 0, max: 65535 No hello_interval Integer min: 1, max: 65535 No network Choice none, p2p, bcastNo passive_ interface Boolean true, falseNo priority Integer min: 0, max: 255 No instance_id Integer min: 0, max: 255 No mtu_ignore Boolean true, falseNo retransmit_ interval Integer min: 1, max: 65535 No transmit_delay Integer min: 1, max: 450 No
Name Type Constraint Mandatory Default Value process String Yes advertise_ secondaries Boolean true, falseNo area String No bfd Boolean true, falseNo cost Integer min: 0, max: 65535 No dead_interval Integer min: 0, max: 65535 No hello_interval Integer min: 1, max: 65535 No network Choice none, p2p, bcastNo passive_ interface Boolean true, falseNo priority Integer min: 0, max: 255 No instance_id Integer min: 0, max: 255 No mtu_ignore Boolean true, falseNo retransmit_ interval Integer min: 1, max: 65535 No transmit_delay Integer min: 1, max: 450 No
Name Type Constraint Mandatory Default Value bfd_instance Boolean true, falseNo dr_priority Integer min: 1, max: 4294967295 No passive Boolean true, falseNo sparse_mode Boolean true, falseNo border Boolean true, falseNo dr_delay Integer min: 1, max: 65535 No jp_policy String No neighbor_policy String No neighbor_ policy_ prefix_ list String No strict_ rfc_ compliant Boolean true, falseNo
Name Type Constraint Mandatory Default Value bfd_instance Boolean true, falseNo dr_priority Integer min: 1, max: 4294967295 No passive Boolean true, falseNo sparse_mode Boolean true, falseNo border Boolean true, falseNo dr_delay Integer min: 1, max: 65535 No jp_policy String No neighbor_ policy_ route_ map String No neighbor_ policy_ prefix_ list String No strict_ rfc_ compliant Boolean true, falseNo
Name Type Constraint Mandatory Default Value instance_name String Yes circuit_type Choice level-1, level-2, level-1-2No ipv4 Boolean true, falseNo ipv6 Boolean true, falseNo network_ point_ to_ point Boolean true, falseNo passive_ interface Choice level-1, level-2, level-1-2, no-level-1, no-level-2, no-level-1-2No metric_level_1 Integer min: 0, max: 16777216 No metric_level_2 Integer min: 0, max: 16777216 No ipv6_ metric_ level_ 1 Integer min: 0, max: 16777216 No ipv6_ metric_ level_ 2 Integer min: 0, max: 16777216 No priority_ level_ 1 Integer min: 0, max: 127 No priority_ level_ 2 Integer min: 0, max: 127 No hello_interval Integer min: 1, max: 65535 No hello_ interval_ level_ 1 Integer min: 1, max: 65535 No hello_ interval_ level_ 2 Integer min: 1, max: 65535 No hello_ multiplier Integer min: 3, max: 1000 No hello_ multiplier_ level_ 1 Integer min: 3, max: 1000 No hello_ multiplier_ level_ 2 Integer min: 3, max: 1000 No hello_padding Choice always, transient, neverNo authentication_ check Boolean true, falseNo authentication_ check_ level_ 1 Boolean true, falseNo authentication_ check_ level_ 2 Boolean true, falseNo authentication_ key_ chain String No authentication_ key_ chain_ level_ 1 String No authentication_ key_ chain_ level_ 2 String No authentication_ type Choice clear, md5, unknownNo authentication_ type_ level_ 1 Choice clear, md5, unknownNo authentication_ type_ level_ 2 Choice clear, md5, unknownNo mtu_check Boolean true, falseNo mtu_ check_ level_ 1 Boolean true, falseNo mtu_ check_ level_ 2 Boolean true, falseNo bfd Boolean true, falseNo ipv6_bfd Boolean true, falseNo csnp_ interval_ level_ 1 Integer min: 1, max: 65535 No csnp_ interval_ level_ 2 Integer min: 1, max: 65535 No lsp_interval Integer min: 10, max: 65535 No retransmit_ interval Integer min: 1, max: 65535 No retransmit_ throttle_ interval Integer min: 20, max: 65535 No mesh_group Integer min: 0, max: 4294967295 No mesh_ group_ blocked Boolean true, falseNo prefix_ attributes_ n_ flag_ clear Boolean true, falseNo suppressed Boolean true, falseNo
Name Type Constraint Mandatory Default Value instance_name String Yes circuit_type Choice l1, l2, l12No ipv4 Boolean true, falseNo ipv6 Boolean true, falseNo network_ point_ to_ point Choice off, on, use-all-is-macNo passive_ interface Choice l1, l2, l12, no-l1, no-l2, no-l12, inherit-defNo metric_level_1 Integer min: 0, max: 16777216 No metric_level_2 Integer min: 0, max: 16777216 No ipv6_ metric_ level_ 1 Integer min: 0, max: 16777216 No ipv6_ metric_ level_ 2 Integer min: 0, max: 16777216 No priority_ level_ 1 Integer min: 0, max: 127 No priority_ level_ 2 Integer min: 0, max: 127 No hello_interval Integer min: 1, max: 65535 No hello_ interval_ level_ 1 Integer min: 1, max: 65535 No hello_ interval_ level_ 2 Integer min: 1, max: 65535 No hello_ multiplier Integer min: 3, max: 1000 No hello_ multiplier_ level_ 1 Integer min: 3, max: 1000 No hello_ multiplier_ level_ 2 Integer min: 3, max: 1000 No hello_padding Choice always, transient, neverNo authentication_ check Boolean true, falseNo authentication_ check_ level_ 1 Boolean true, falseNo authentication_ check_ level_ 2 Boolean true, falseNo authentication_ key_ chain String No authentication_ key_ chain_ level_ 1 String No authentication_ key_ chain_ level_ 2 String No authentication_ type Choice clear, md5, unknownNo authentication_ type_ level_ 1 Choice clear, md5, unknownNo authentication_ type_ level_ 2 Choice clear, md5, unknownNo mtu_check Boolean true, falseNo mtu_ check_ level_ 1 Boolean true, falseNo mtu_ check_ level_ 2 Boolean true, falseNo bfd Boolean true, falseNo ipv6_bfd Boolean true, falseNo csnp_ interval_ level_ 1 Integer min: 1, max: 65535 No csnp_ interval_ level_ 2 Integer min: 1, max: 65535 No lsp_interval Integer min: 10, max: 65535 No retransmit_ interval Integer min: 1, max: 65535 No retransmit_ throttle_ interval Integer min: 20, max: 65535 No mesh_group Integer min: 0, max: 4294967295 No mesh_ group_ blocked Boolean true, falseNo n_flag_clear Boolean true, falseNo suppress_prefix Boolean true, falseNo
Name Type Constraint Mandatory Default Value interval Integer min: 0, max: 999 No min_rx Integer min: 0, max: 999 No multiplier Integer min: 0, max: 50 No echo Boolean true, falseNo echo_ rx_ interval Integer min: 0, max: 999 No optimize_ subinterface Boolean true, falseNo per_link Boolean true, falseNo source_ip IP No vpc_watch Boolean true, falseNo track_ member_ link Boolean true, falseNo authentication_ type Choice none, keyed-sha1, meticulous-keyed-sha1No authentication_ key_ id Integer min: 1, max: 255 No authentication_ key String No authentication_ interop Boolean true, falseNo
Name Type Constraint Mandatory Default Value interval Integer min: 0, max: 999 No min_rx Integer min: 0, max: 999 No multiplier Integer min: 0, max: 50 No echo Boolean true, falseNo echo_ rx_ interval Integer min: 0, max: 999 No optimize_ subinterface Boolean true, falseNo per_link Boolean true, falseNo source_ip String No vpc_watch Boolean true, falseNo track_ member_ link Boolean true, falseNo authentication_ type Choice none, sha1, met-sha1No authentication_ key_ id Integer min: 1, max: 255 No authentication_ key String No authentication_ interop Boolean true, falseNo
Name Type Constraint Mandatory Default Value ra_bootfile_url String No suppress_ra Boolean true, falseNo suppress_ra_mtu Boolean true, falseNo managed_ config_ flag Boolean true, falseNo other_ config_ flag Boolean true, falseNo redirects Boolean true, falseNo dad_attempts Integer min: 0, max: 15 No dadns_interval Integer min: 1000, max: 6000 No delete_ adj_ on_ mac_ delete Boolean true, falseNo ra_ dns_ search_ list_ suppress Boolean true, falseNo ra_ dns_ server_ suppress Boolean true, falseNo hop_limit Integer min: 0, max: 255 No mac_extract Choice none, nud-phase, exclude-nud-phaseNo mtu Integer min: 1280, max: 65535 No ns_interval Integer min: 1000, max: 3600000 No ra_interval Integer min: 4, max: 1800 No ra_ interval_ minimum Integer min: 3, max: 1350 No ra_lifetime Integer min: 0, max: 9000 No reachable_time Integer min: 0, max: 3600000 No retrans_timer Integer min: 0, max: 4294967295 No ra_ route_ suppress Boolean true, falseNo router_ preference Choice low, medium, highNo
Name Type Constraint Mandatory Default Value ra_ boot_ file_ url String No suppress_ra Boolean true, falseNo suppress_ra_mtu Boolean true, falseNo managed_ config_ flag Boolean true, falseNo other_ config_ flag Boolean true, falseNo redirects Boolean true, falseNo dad_attempts Integer min: 0, max: 15 No dad_ns_interval Integer min: 1000, max: 6000 No delete_ adjacency_ on_ mac_ delete Boolean true, falseNo dns_ search_ list_ suppress Boolean true, falseNo dns_suppress Boolean true, falseNo hop_limit Integer min: 0, max: 255 No mac_extract Choice none, nud-phase, exclude-nud-phaseNo mtu Integer min: 1280, max: 65535 No ns_interval Integer min: 1000, max: 3600000 No ra_interval Integer min: 4, max: 1800 No ra_ interval_ minimum Integer min: 3, max: 1350 No ra_lifetime Integer min: 0, max: 9000 No reachable_time Integer min: 0, max: 3600000 No retrans_timer Integer min: 0, max: 4294967295 No suppress_ ra_ route Boolean true, falseNo router_ preference Choice unspecified, low, medium, highNo
Name Type Constraint Mandatory Default Value address IP Yes tag Integer min: 0, max: 4294967295 No
Name Type Constraint Mandatory Default Value address IP Yes vrf String No
Name Type Constraint Mandatory Default Value address String Yes vrf String No
Name Type Constraint Mandatory Default Value address IP Yes type Choice primary, secondaryNo tag Integer min: 0, max: 4294967295 No eui64 Boolean true, falseNo route_ preference Integer min: 0, max: 255 No
Name Type Constraint Mandatory Default Value address String Yes type Choice primary, secondaryNo tag Integer min: 0, max: 4294967295 No eui64 Boolean true, falseNo route_ preference Integer min: 0, max: 255 No
Name Type Constraint Mandatory Default Value address IP Yes vrf String No
Name Type Constraint Mandatory Default Value address String Yes vrf String No
Example 1: Router-ID loopback with OSPF and PIM using an interface group
interface_groups : [ LOOPBACK_INTERFACE ]
Example 2: VTEP source loopback and anycast RP loopback for a VXLAN fabric
interface_groups : [ LOOPBACK_INTERFACE ]
interface_groups : [ LOOPBACK_INTERFACE ]
interface_groups : [ LOOPBACK_INTERFACE ]
interface_groups : [ LOOPBACK_INTERFACE ]
Example 3: Loopback with inline OSPF/PIM configuration and VRF membership
description : Router-ID-Underlay
description : VRF-BLUE-Loopback
- address : 2001:db8:1::1/128