Design Flashcards
what are attributes of vxlan multipod?
Underlay
• Nicely Structured and Tiered Topologies
• Allows Efficient Scale-Out
• More End-Points = More Leaf
• More Bandwidth, Resilience or Capacity = More Spine or Tiers
• Different Control-Plane Instances (BGP AS)
- Overlay
- End-to-End Encapsulation, Flat, No Hierarchy
- Single Control-Plane ”reach” – all in one ”kitchen sink”
what are attributes of vxlan multi-site?
Multiple Overlay Domains • Per-Site Encapsulation • Closest to the Source • Closest to the Destination • Exit/Transit via Border Gateway (BGW) • Multi-Site and/or External Connectivity • @ Leaf = Border Leaf • @ Spine = Border Spine • Super-Spine becomes Transit
what are best practices for ip-addressing when building a vxlan fabric?
Separate Interface functions through IP Addressing (Aggregates) Example: • Unicast Routing – Routing Protocol Peering (p2p*) --> 10.0.0.0/24 • Unicast Routing – Routing Identifier (RID) --> 100.0.0.0/24 • VTEP and VPC --> 200.0.0.0/24 • Multicast Rendezvous-Point (RP) --> 20.0.0.0/24
which configuration is mandatory on N56K switches to be able to configure vxlan?
switch must be configured to use store-and-forward switching instead of cut-through, needs a reload
hardware ethernet store-and-fwd-switching
what is the actual TEP on your switch, that encap/decap vxlan frames?
interface nve
what are use-cases for vxlan evpn multi-site?
scaling, compartmentalization (reduce failure domains) and DCI.
In addition you can control what (which VLAN, VRF) will be extended between sites
what are hardware and software requirements for the BGW function?
Cisco Nexus hardware
● Cisco Nexus 9300 EX platform ● Cisco Nexus 9300 FX platform ● Cisco Nexus 9300 FX2 platform ● Cisco Nexus 9300-GX platform * ● Cisco Nexus 9332C platform ● Cisco Nexus 9364C platform ● Cisco Nexus 9500 platform with X9700-EX line card ● Cisco Nexus 9500 platform with X9700-FX line card Cisco NX-OS Software
Cisco NX-OS Software Release 7.0(3)I7(1) or later
what is the main functional component of vxlan evpn multi-site?
The main functional component of the EVPN Multi-Site architecture is the border gateway, or BGW. BGWs separate the fabric-side (site-internal fabric) from the network that interconnects the sites (site-external DCI) and mask the site-internal VTEPs.
will the transport network between sites see the site-internal VTEPs to enable transportation of vxlan packets?
no, Only the underlay IP addresses of the BGWs are seen inside the transport network between the BGWs. The site-internal VTEPs are always masked behind the BGWs.
of which functions must the site-internal node (SPINE) be capable in multi-site, connecting to BGW?
● VXLAN with Protocol-Independent Multicast (PIM) Any-Source Multicast (ASM) or ingress replication (BGP EVPN Route Type 3) in the underlay
● BGP EVPN Route Type 2 and Route Type 5 for the overlay control plane
● Route reflector capable of exchanging BGP EVPN Route Type 4
● VXLAN Operations, Administration, and Maintenance (OAM)–capable devices for end-to-end OAM support
can you use PIM BiDir in vxlan evpn multi-site?
no, it must be PIM ASM or head-end replication
how will BGWs send BUM traffic between sites
head-end-replication
where can you place BGWs in the fabric?
BGW could be either a dedicated pair of leaves or directly connected to the SPINEs or the BGW function can be configured on the SPINEs direclty.
what is a design drawback of having the BGW function on the SPINEs?
If the BGW is on the spine, many functions are overloaded together: for instance, route-reflector, Rendezvous-Point (RP), east-west traffic, and external connectivity functions. In this case, you need to consider additional factors related to scale, configuration, and failure scenarios.
what are the design options for BGW in regards to redundancy?
can be either vPC pair or anycast-BGW
which platform do you need for anycast-BGW?
N9K cloud-scale (EX or FX)
how many anycast-BGW per site are supported?
4 A-BGW as per 7.x
can you use an ethernet-interface-ip-address as anycast-BGW address?
no, The virtual IP address is represented by a dedicated loopback interface associated with the Network Virtualization Endpoint (NVE) interface (multisite border-gateway interface loopback100).
what is a “PIP” and what is PIP’s function?
In addition to the virtual IP address or anycast IP address, every BGW has its own individual personality represented by the primary VTEP IP (PIP) address (source-interface loopback1). The PIP address is responsible in the BGW for handling BUM traffic. Every BGW uses its PIP address to perform BUM replication, either in the multicast underlay or when advertising BGP EVPN Route Type 3 (inclusive multicast), used for ingress replication.
If the BGW is providing external connectivity with VRF-lite next to the EVPN Multi-Site deployment, routing prefixes that are learned from the external Layer 3 devices are advertised inside the VXLAN fabric with the PIP address as the next-hop address
will every BGW forward all BUM traffic in anycast-BGW scenario?
No, Every A-BGW actively participates in the forwarding of BUM traffic. Specifically, the Designated-Forwarder (DF) function for BUM traffic is distributed on a per–Layer 2 VXLAN Network Identifier (VNI) basis. To synchronize the designated forwarders, BGP EVPN Route Type 4 (Ethernet segment route) updates are exchanged between the BGWs within the same site (Figure 6).
what is a requirement to participate in designated-forwarder election in anycast-BGW scenario?
To participate in the designated-forwarder election, the configuration of the same site ID is required. This ID is defined as part of the BGW configuration (evpn multisite border-gateway ). In addition to the site ID, the use the same Layer 2 VNI is needed to elect the designated forwarder from among the eligible BGWs.
what are the two main failure-scenarios in evpn multi-site BGW?
site-internal or site-external failure
how will BGW recognize site-internal failure and how will it react?
evpn multisite fabric-tracking
The EVPN Multi-Site fabric-tracking function detects whether one or all of the site-internal interfaces are available. As long as one of these interfaces is operational and available, the BGW can extend Layer 2 and Layer 3 traffic to remote sites. If all fabric-tracking interfaces are reported to be down, the following steps are performed:
● The isolated BGW stops advertising the virtual IP address to the site-external underlay network.
● The isolated BGW withdraws all of its advertised BGP EVPN routes (Route Type 2, Route Type 3, Route Type 4, and Route Type 5).
● The remaining BGWs withdraw all BGP EVPN Route Type 4 (Ethernet segment) routes received from the now isolated BGW because reachability is missing.
how will BGW detect site-external failure and how will it react?
evpn multisite dci-tracking
In the rare case in which all DCI-tracking interfaces are down, the BGW performs the following actions:
● It stops advertising the virtual IP address to the site-internal underlay network.
● It withdraws all BGP EVPN Route Type 4 (Ethernet segment) route advertisement.
● It converts the BGW to a traditional VTEP (the PIP address stays up).
