- Overlay transport virtualization (OTV)
- OTV timers
- Multicast transport
- Unicast transport
- OTV IS-IS
- FHRP
Overlay transport virtualization (OTV)
- IS-IS, UDP 8472, GRE + MPLS (AToM)
- MAC-in-UDP
- data plane learning
- does not forward BPDU, unknown unicast
- ARP snooping
- local ARP response
- ARP aging must be lower that CAM aging
- site VLAN
- used to discover OTV edge on the same site
- must not be in OTV
- 1 site ≡ 1 site ID (part of IS-IS Hello)
- authoritative edge device (AED)
- OTV edge in Active state
- election:
- order number of AED – N: from highest to lowest system ID
- if VLAN % edges = N, then edge N is AED
- adjacency
- site adjacency: site VLAN
- overlay adjacency: over Join interface
- neighbour ID = site ID + IS-IS ID
- MTU += 42 bytes, DF bit
- strips CRC and 802.1Q from frame: present in OTV header
- CoS → shim header → CoS
- inner DSCP → outer DSCP →× inner DSCP
- incompatible with SVI (requires separate VDC)
(config)# feature otv
(config)# otv site-identifier <ID>
; VLAN 1 default
(config)# otv site-vlan <N>
; permit unknown unicast flood for specific MAC
(config)# otv flood mac <MAC> vlan <VLAN>
(config)# interface overlay <N>
(config-if-overlay)# otv join-interface <INTF>
; VLANs over OTV
(config-if-overlay)# otv extend-vlan <VLAN_LIST>
; on default
(config-if-overlay)# otv suppress-arp-nd
# show otv overlay
# show otv adjacency
OTV timers
- ARP aging: 480s default
- CAM aging: 1800s default
- stale entry: 600s default
- if adjacency server fails, time to store entry in cache
- not triggered by IS-IS peer not refreshing its entry
; 8 mins default
(config-if-overlay)# otv arp-nd timeout <sec>
Multicast transport
- IGMPv3, not PIM
- ASM for control protocol (discovery, MAC exchange), bcast
- SSM for mcast data traffic
- PIM-BD in core
- source edge creates mapping between SSM and mcast group: src VLAN and edge IP
- destination edge sends GM-Update to source edge to update OIL
; ASM
(config-if-overlay)# otv control-group <ADDR>
; SSM range
(config-if-overlay)# otv data-group <RANGE>
Unicast transport
- head-end replication on all edges to all edges
- adjacency server
- discovery only, does not participate in HREP
- OTV edge list timeout – 10 mins
- source edge announces source VLAN, mcast group, edge IP
- destination edge sends GM-Update to source edge to update OIL
- Overlay interface number ≡ VPN ID must match
; unicast transport, primary server
(config-if-overlay)# otv adjacency-server unicast-only
; unicast transport, secondary server
(config-if-overlay)# otv use-adjacency-server <IP1> unicast-only
; unicast transport, edge
(config-if-overlay)# otv use-adjacency-server <IP1> <IP2> unicast-only
OTV IS-IS
- installs MAC in CAM on non-AED to accelarate convergence
- non-AED create (S,G) for local source, send Join when receiver activates, but do no send actual traffic (AED responsibility)
FHRP
- must be filtered, otherwise single GW for all sites or MAC flap
(config)# mac-list <LIST> seq <N> permit|deny <MAC> <MASK>
(config)# route-map <RMAP>
(config-route-map)# match mac-list <LIST>
(config)# otv-isis default
(config-router)# vpn Overlay1
(config-router-vrf)# redistribute filter route-map <RMAP>