What does a typical branch office network look like?
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A small, standard version of the campus: one edge device (router, SD-WAN appliance or firewall) with a WAN or internet link and usually a backup link or LTE, one or two PoE access switches, a few APs, and VLANs for users, voice, wireless, guest and management. Most services stay central or in the cloud, with enough local function to keep working when the WAN is down. Every branch is built from the same template.
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Building blocks
- Edge: router or SD-WAN edge, often with the firewall built in. Encrypted tunnels to the hubs or the cloud.
- LAN: a PoE switch or small stack, the gateway SVIs on the edge or on a layer 3 switch.
- Wireless: cloud-managed APs, or controller APs with local switching so traffic does not hairpin to a central controller.
- Services: DHCP local on the edge or relayed to central servers, DNS forwarding, NTP.
Decisions that matter
- Internet breakout: local breakout for SaaS and internet is now common; backhaul everything only if central inspection is mandatory and the WAN can carry it.
- Survivability: what still works if the WAN fails? Local DHCP, cached DNS, voice survivability (SRST on Cisco) so phones can still call locally and out a local line if one exists.
- Standardization: same VLAN IDs, same address layout, same config template. Zero-touch provisioning so a non-specialist can install the hardware.
- Security: guest goes straight to the internet; edge ports use 802.1X or MAB like the campus.
Traps
- Designing each branch by hand. At 50 branches, consistency matters more than per-site optimization.
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