diff --git a/README.md b/README.md
index 3c63919..03af3b1 100644
--- a/README.md
+++ b/README.md
@@ -314,6 +314,40 @@ lldp2map/
 - [github.com/gosnmp/gosnmp](https://github.com/gosnmp/gosnmp) — SNMP v2c/v3
 - [github.com/spf13/cobra](https://github.com/spf13/cobra) — CLI framework
 
+## Linux lldpd and SNMP
+
+Linux hosts running [`lldpd`](https://lldpd.github.io) do **not** expose LLDP neighbor data via SNMP by default. `lldpd` must be configured to operate as an AgentX sub-agent alongside `snmpd`. Without this, lldp2map can still discover a Linux host as a *neighbor* (seen from an adjacent device's LLDP table), but it cannot recurse into that host to find *its* neighbors.
+
+This is particularly useful on operating systems like proxmox which also house LXCs and VMs that may also be running lldpd. I don't know if this works on VMWare or HyperV, or if lldp is exposed under windows, althugh it [can be enabled](https://learn.microsoft.com/en-us/powershell/module/netlldpagent/enable-netlldpagent?view=windowsserver2025-ps).
+
+To enable SNMP on a Linux host running `lldpd`:
+
+1. Install and configure `snmpd`, then add AgentX master support to `/etc/snmp/snmpd.conf`:
+
+```text
+master agentx
+```
+
+1. Start `lldpd` with the `-x` flag to connect as an AgentX sub-agent:
+
+```bash
+lldpd -x
+```
+
+Or, in `/etc/default/lldpd` (Debian/Ubuntu) or `/etc/sysconfig/lldpd` (RHEL/Fedora):
+
+```text
+DAEMON_ARGS="-x"
+```
+
+1. Restart both services:
+
+```bash
+systemctl restart snmpd lldpd
+```
+
+Once configured, lldp2map can walk the LLDP-MIB on the Linux host just like any other device.
+
 ## Caveats
 
 - Neighbors with no resolvable IP (no management address, no chassis networkAddress, and no ARP/NDP entry for their MAC) are added to the map but not recursed into. The discovery log explicitly reports this for each such neighbor.
diff --git a/cmd/root.go b/cmd/root.go
index bd789ba..cc30361 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -10,17 +10,17 @@ import (
 )
 
 var (
-	community    string
-	snmpVersion  string
-	username     string
-	authProto    string
-	authPass     string
-	privProto    string
-	privPass     string
-	secLevel     string
-	snmpPort     uint16
-	snmpTimeout  int
-	snmpRetries  int
+	community        string
+	snmpVersion      string
+	username         string
+	authProto        string
+	authPass         string
+	privProto        string
+	privPass         string
+	secLevel         string
+	snmpPort         uint16
+	snmpTimeout      int
+	snmpRetries      int
 	maxHops          int
 	showAddrs        bool
 	addrFamily       string
@@ -100,6 +100,14 @@ func init() {
 func run(_ *cobra.Command, args []string) error {
 	seedHost := args[0]
 
+	// Validate --addr-family early so the user gets a clear error before
+	// any SNMP connections are attempted.
+	switch addrFamily {
+	case "ipv4", "ipv6", "both":
+	default:
+		return fmt.Errorf("invalid --addr-family %q: must be ipv4, ipv6, or both", addrFamily)
+	}
+
 	validFormats := map[string]string{
 		"png":        ".png",
 		"pdf":        ".pdf",
diff --git a/internal/discover/discover.go b/internal/discover/discover.go
index 7bceabc..3a38254 100644
--- a/internal/discover/discover.go
+++ b/internal/discover/discover.go
@@ -116,6 +116,13 @@ func Run(ctx context.Context, cfg Config, log func(string)) (*graph.Topology, er
 
 		if err != nil {
 			log(fmt.Sprintf("%s  Warning: LLDP walk failed on %s: %v", indent, item.host, err))
+			// Preserve the node even on a partial walk failure so that the
+			// device appears in the topology (it was reachable via SNMP).
+			nodeName := item.host
+			if info != nil && info.SysName != "" {
+				nodeName = info.SysName
+			}
+			topo.AddNode(nodeName, item.host)
 			continue
 		}
 
@@ -157,8 +164,14 @@ func Run(ctx context.Context, cfg Config, log func(string)) (*graph.Topology, er
 				continue
 			}
 
+			filteredAddrs := filter.IPs(neighbor.MgmtAddrs, cfg.AddrFamily, ignorePrefixes)
+			if len(filteredAddrs) == 0 && len(neighbor.MgmtAddrs) > 0 {
+				log(fmt.Sprintf("%s      (all %d management address(es) excluded by addr-family/ignore-prefix filter)", indent, len(neighbor.MgmtAddrs)))
+				continue
+			}
+
 			queued := 0
-			for _, ip := range filter.IPs(neighbor.MgmtAddrs, cfg.AddrFamily, ignorePrefixes) {
+			for _, ip := range filteredAddrs {
 				ipStr := ip.String()
 				if !visited[ipStr] && !inQueue(queue, ipStr) {
 					queue = append(queue, queueItem{host: ipStr, depth: item.depth + 1})
@@ -168,7 +181,7 @@ func Run(ctx context.Context, cfg Config, log func(string)) (*graph.Topology, er
 				}
 			}
 			if queued == 0 {
-				log(fmt.Sprintf("%s      (all %d address(es) already visited/queued)", indent, len(neighbor.MgmtAddrs)))
+				log(fmt.Sprintf("%s      (all %d management address(es) already visited or queued)", indent, len(filteredAddrs)))
 			}
 		}
 	}
diff --git a/internal/lldp/walker.go b/internal/lldp/walker.go
index c421487..e01c4f8 100644
--- a/internal/lldp/walker.go
+++ b/internal/lldp/walker.go
@@ -42,6 +42,11 @@ const (
 	// ARP table — IPv4 MAC→IP mapping on the queried device.
 	// Index: ifIndex.a.b.c.d  Value: MAC (6 bytes)
 	oidARPPhysAddr = "1.3.6.1.2.1.4.22.1.2"
+
+	// ipNetToPhysicalTable (RFC 4293) — unified IPv4+IPv6 neighbor table.
+	// Index: ifIndex.addrType.addrLen.addr[bytes]  Value: MAC (6 bytes)
+	// addrType 1=IPv4 (4 bytes), 2=IPv6 (16 bytes)
+	oidIPNetToPhysicalPhysAddr = "1.3.6.1.2.1.4.35.1.4"
 )
 
 // Neighbor represents a single LLDP-discovered neighbor.
@@ -85,7 +90,9 @@ func Walk(client *snmpclient.Client) (*LocalInfo, error) {
 	sysNames := map[remKey]string{}
 	pdus, err := client.Walk(oidRemSysName)
 	if err != nil {
-		return nil, fmt.Errorf("walk lldpRemSysName: %w", err)
+		// Return whatever partial info we have so the caller can still register
+		// this node in the topology even if the full LLDP walk fails.
+		return info, fmt.Errorf("walk lldpRemSysName: %w", err)
 	}
 	for _, pdu := range pdus {
 		if k, ok := parseRemKey(pdu.Name, oidRemSysName); ok {
@@ -165,12 +172,17 @@ func Walk(client *snmpclient.Client) (*LocalInfo, error) {
 		}
 	}
 
-	// For MAC-identified chassis IDs, look up the matching IP in the device's ARP table.
+	// For MAC-identified chassis IDs, resolve to an IP address.
+	// Prefer the RFC 4293 unified IPv4+IPv6 neighbor table; fall back to the
+	// legacy IPv4-only ARP table for devices that don't implement RFC 4293.
 	if len(chassisMACs) > 0 {
-		arpMap := walkARP(client)
+		neighborMap := walkIPNetToPhysical(client)
+		if len(neighborMap) == 0 {
+			neighborMap = walkARP(client)
+		}
 		for k, mac := range chassisMACs {
 			if _, already := chassisIPs[k]; !already {
-				if ip, found := arpMap[mac]; found {
+				if ip, found := neighborMap[mac]; found {
 					chassisIPs[k] = ip
 				}
 			}
@@ -335,6 +347,67 @@ func walkARP(client *snmpclient.Client) map[[6]byte]net.IP {
 	return result
 }
 
+// walkIPNetToPhysical walks the RFC 4293 ipNetToPhysicalTable, which contains
+// both IPv4 (ARP) and IPv6 (NDP) neighbor entries. Returns a MAC→IP map
+// preferring a global-unicast IPv6 address over IPv4 when both are present
+// for the same MAC. Loopback and link-local addresses are excluded.
+// Index format: ifIndex.addrType.addrLen.addr[bytes]  Value: MAC (6 bytes)
+func walkIPNetToPhysical(client *snmpclient.Client) map[[6]byte]net.IP {
+	result := map[[6]byte]net.IP{}
+	pdus, err := client.Walk(oidIPNetToPhysicalPhysAddr)
+	if err != nil {
+		return result
+	}
+	for _, pdu := range pdus {
+		suffix := suffixAfter(pdu.Name, oidIPNetToPhysicalPhysAddr)
+		if suffix == "" {
+			continue
+		}
+		parts := strings.Split(suffix, ".")
+		// Minimum: ifIndex(1) addrType(1) addrLen(1) addr(>=4) = 7 parts for IPv4.
+		if len(parts) < 7 {
+			continue
+		}
+		addrType := parts[1] // 1=IPv4, 2=IPv6
+
+		var ip net.IP
+		switch addrType {
+		case "1": // IPv4: addrLen always 4, addr starts at parts[3]
+			if len(parts) >= 7 {
+				ip = net.ParseIP(strings.Join(parts[3:7], "."))
+			}
+		case "2": // IPv6: addrLen always 16, addr starts at parts[3]
+			if len(parts) >= 19 {
+				b := make([]byte, 16)
+				for i := 0; i < 16; i++ {
+					var v int
+					fmt.Sscanf(parts[3+i], "%d", &v)
+					b[i] = byte(v)
+				}
+				ip = net.IP(b)
+			}
+		}
+
+		if ip == nil || ip.IsLoopback() || ip.IsLinkLocalUnicast() {
+			continue
+		}
+
+		mac, ok := pdu.Value.([]byte)
+		if !ok || len(mac) != 6 {
+			continue
+		}
+		var key [6]byte
+		copy(key[:], mac)
+
+		// Prefer global-unicast IPv6 over IPv4 when multiple entries share a MAC.
+		existing, has := result[key]
+		if !has || (existing.To4() != nil && ip.To4() == nil) {
+			result[key] = ip
+		}
+	}
+	return result
+}
+
 // WalkIPAddresses returns all non-loopback, non-link-local unicast interface
 // addresses on the device. It queries the modern ipAddressTable (RFC 4293)
 // which covers both IPv4 and IPv6, falling back to the legacy IPv4-only